VSAT Manual

This document contains proprietary information and shall not be reproduced in whole or in part without the prior written permission of Powertech.

VSAT Voltage Security Assessment Tool

User Manual

A product of

Powertech Labs Inc. Surrey, British Columbia Canada www.powertechlabs.com www.DSATools.com

http://www.powertechlabs.com/

http://www.dsatools.com/

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Powertech Labs Inc. i

DISCLAIMER OF WARRANTIES AND LIMITATION OF LIABILITIES THIS SOFTWARE AND ITS DOCUMENTATION WERE PREPARED BY POWERTECH LABS, INC. (PLI). NEITHER PLI, ANY COSPONSOR, NOR ANY PERSON ACTING ON BEHALF OF ANY OF THEM: (A) MAKES ANY WARRANTY OR REPRESENTATION WHATSOEVER, EXPRESS OR IMPLIED,

(I) WITH RESPECT TO THE USE OF ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS DOCUMENT, INCLUDING MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, OR (II) THAT SUCH USE DOES NOT INFRINGE ON OR INTERFERE WITH PRIVATELY OWNED RIGHTS, INCLUDING ANY PARTY'S INTELLECTUAL PROPERTY, OR (III) THAT THIS DOCUMENT IS SUITABLE TO ANY PARTICULAR USER'S CIRCUMSTANCE; OR

(B) ASSUMES RESPONSIBILITY FOR ANY DAMAGES OR OTHER LIABILITY WHATSOEVER (INCLUDING ANY CONSEQUENTIAL DAMAGES, EVEN IF PLI OR ANY PLI REPRESENTATIVE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES) RESULTING FROM YOUR SELECTION OR USE OF THIS DOCUMENT OR ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS DOCUMENT.

VSAT program and its documentation are confidential property of Powertech Labs Inc. This Program is protected under the copyright laws and by application of international treaties. All Rights Reserved under the Copyright Laws. Except as expressly provided by the terms and conditions set forth in the License, the LICENSEE shall not:

(a) distribute or disclose the Program, Documentation or Derivative Work thereof to others; or (b) disclose the Proprietary Information associated with or embodied in the Program and

Documentation in any form whatsoever; Without prior written consent of Powertech Labs Inc. The LICENSEE shall not use the program except as expressly provided by the conditions of LICENSE TYPE in the License.

Copyright Powertech Labs Inc. 2001−−−−2011

Last modified – April 2011

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Powertech Labs Inc. ii

CONTENTS

1. Program Installation and Testing ........................................................................... 1

1.1 Minimum System Requirements ....................................................................... 1

1.2 Installing VSAT ................................................................................................. 1

1.3 Installing Protection Dongles ............................................................................ 2

1.4 Included Files ................................................................................................... 5

1.5 Running VSAT Test Cases ............................................................................... 5

1.6 User Support Information .................................................................................. 8

2. Overview .................................................................................................................. 9

2.1 VSAT Description ............................................................................................. 9

2.2 Security Assessment Module ............................................................................ 9

2.2.1 Secure Range....................................................................................................... 9

2.2.2 Secure Region .................................................................................................... 10

2.2.3 Modal Analysis ................................................................................................... 10

2.2.4 VQ Curve Computation ...................................................................................... 11

2.3 Contingency Screening Module ...................................................................... 11

2.4 Modeling of System Protection Schemes........................................................ 11

2.5 Remedial Action Module ................................................................................. 12

2.6 Distributed Processing .................................................................................... 12

2.7 Scenarios and Data Files ................................................................................ 13

2.7.1 The Scenario Concept ........................................................................................ 13

2.7.2 Data Files ........................................................................................................... 13

2.8 Computation Process ..................................................................................... 18

2.8.1 Contingency Screening Process ........................................................................ 21

2.9 VSAT Structure............................................................................................... 22

2.9.1 VSAT Main Window ........................................................................................... 22

3. Setting Up Scenarios ............................................................................................ 24

3.1 Preparing the Scenarios Manually .................................................................. 24

3.1.1 Preparing the Data Files ..................................................................................... 24

3.1.2 Preparing the Scenario File ................................................................................ 24

3.1.3 Preparing the Master Scenario File .................................................................... 25

3.2 Preparing the Scenarios through VSAT GUI ................................................... 26

3.2.1 Creating a New Scenario ................................................................................... 26

3.2.2 Adding Existing Scenario Files ........................................................................... 28

3.2.3 Modifying Scenarios and Data Files ................................................................... 29

3.2.4 Removing Scenarios .......................................................................................... 31

3.2.5 Viewing Powerflow Data ..................................................................................... 31

3.2.6 Compare Scenarios ............................................................................................ 31

3.2.7 Archiving Scenarios ............................................................................................ 31

3.2.8 Creating and Saving a Master Scenario (or Case) FILE .................................... 31

3.2.9 Adding Scenarios Using a Master Scenario File ................................................ 32

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3.2.10 Archiving All Scenarios ....................................................................................... 32

3.2.11 Exiting VSAT ...................................................................................................... 32

3.3 Powerflow Data and Conversion to PFB ......................................................... 32

3.4 Data Views ..................................................................................................... 33

3.4.1 General Features of Data Views ........................................................................ 33

3.4.2 Parameter Data View ......................................................................................... 35

3.4.3 Transfer Data View ............................................................................................. 36

3.4.4 Contingency Script View .................................................................................... 38

3.4.5 Contingency Data View ...................................................................................... 40

3.4.6 Generator Capability Data View ......................................................................... 41

3.4.7 Load Conversion Data View ............................................................................... 42

3.4.8 Generator Coupling Data View ........................................................................... 43

3.4.9 Other Data Views ............................................................................................... 44

4. Running VSAT ....................................................................................................... 45

4.1 Starting and Controlling the Servers ............................................................... 45

4.2 Converting Powerflow Data ............................................................................ 47

4.3 Screening Contingencies ................................................................................ 48

4.4 Enabling/Disabling Scenarios ......................................................................... 51

4.5 Running the Security Assessment .................................................................. 51

4.6 Viewing the Limits and Violations ................................................................... 52

4.7 Viewing the Messages .................................................................................... 54

4.8 Viewing and Plotting the Results .................................................................... 55

4.9 Running VSAT Batch ...................................................................................... 55

5. Remedial Action .................................................................................................... 57

5.1 RA Data Requirement..................................................................................... 57

5.2 Running RA .................................................................................................... 58

6. Distributed Processing Setup .............................................................................. 60

6.1 Stand-alone Network Connection ................................................................... 60

6.2 Existing Network Connection .......................................................................... 61

6.3 Configuring Networked Computers ................................................................. 61

6.4 Configuring Stand-alone Computer................................................................. 62

6.5 Setting up Multiple Servers on a Single PC .................................................... 63

7. Output Files ........................................................................................................... 64

8. Input Data File Formats ........................................................................................ 65

8.1 General Rules ................................................................................................ 65

8.1.1 Data File Structure ............................................................................................. 65

8.1.2 Data Records ...................................................................................................... 66

8.1.3 Name Option ...................................................................................................... 66

8.1.4 Include and Exclude Records ............................................................................. 67

8.2 Powerflow File – PFB (or PSF) Format ........................................................... 68

8.3 Powerflow File – Third Party Format ............................................................... 68

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8.4 Parameter File ................................................................................................ 68

8.5 Transfer File ................................................................................................... 79

8.6 Criteria File ..................................................................................................... 93

8.7 Margin File ...................................................................................................... 97

8.8 Monitored Variable File ................................................................................. 101

8.9 Contingency Script File ................................................................................. 109

8.10 Contingency File ........................................................................................... 111

8.11 Contingency Screening Parameter File ........................................................ 117

8.12 Interface and Circuit File ............................................................................... 119

8.13 Generator Capability File .............................................................................. 121

8.14 Governor Response File ............................................................................... 126

8.15 AGC Action File ............................................................................................ 127

8.16 Load Conversion File .................................................................................... 131

8.17 Load Swap File ............................................................................................. 134

8.18 Branch Rating File ........................................................................................ 134

8.19 Modal Analysis Parameter File ..................................................................... 136

8.20 VQ Curve File ............................................................................................... 138

8.21 Control Mode File ......................................................................................... 139

8.22 System Protection Schemes (SPS) File ........................................................ 143

8.22.1 General ............................................................................................................. 143

8.22.2 Conditions ......................................................................................................... 144

8.22.3 Actions .............................................................................................................. 144

8.22.4 SPS Data Format ............................................................................................. 144

8.23 Remedial Control File ................................................................................... 153

8.24 Sensitivity Parameter File ............................................................................. 160

8.25 Generator Coupling File ................................................................................ 163

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1. Program Installation and Testing

This chapter describes program installation and testing on Windows, XP, Vista, and 7 systems.

1.1 Minimum System Requirements

The minimum hardware and software requirements for VSAT are: (1) Pentium4 CPU or higher (2) 100 MB of free hard disk space (3) 1 GB of RAM (4) XP, Vista, or Windows 7 operating system (5) Acrobat Reader 7 for viewing the manuals

1.2 Installing VSAT

Running the installation program provided on the VSAT CD creates the necessary folders and files on your computer. To install the software:

(1) Place the CD in your CD drive. After a few seconds, the Powertech Software Installation Guide window will appear on your screen. In this case go to step 3, otherwise go to step 2.

(2) To open the Powertech Software Installation Guide window, from the Start menu of your computer

select Run and type:

X:\start.exe

Where X is the drive in which the VSAT CD is inserted (e.g. D:\start.exe)

(3) Click on Install DSA Software (or run the setup.exe program from the CD) to install VSAT. When

the DSA installer window appears, follow the steps as shown on your screen to complete the installation. The installation steps are:

• Display of program information and welcome message.

• Display of License Agreement: You must accept the terms of license to complete the installation.

• Display of installation information.

• Selection of destination folder: By default, the installation program creates a directory named C:\DSATools_x\VSAT (or, C:\DSATools_xnet\VSAT for network version) where x is the version number. You may change this default destination to other directories/drives.

Note: If you have a previous version of VSAT installed on your computer, you don’t need to uninstall it before installing the latest version.

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1.3 Installing Protection Dongles

Dongle types

There are two types of dongles:

• Single-user dongles. A single-user dongle allows the unlimited application sessions for all enabled applications on the computer where it is attached.

• Network dongles. A network dongle allows the specified application sessions for all enabled applications on all computers in the same LAN as the computer where it is attached. The number of sessions allowed for a normal DSATools network dongle is 10. This means that if you have started PSAT and VSAT on your computer with this dongle, there will be 8 additional sessions available for other users to use.

Depending on the license type that you have, you may have one or both of these dongles. Note that VSAT is released in two versions: a single-user version that works with single-user dongles and a network version that works with network dongles. The following modules in the VSAT package require the dongle to run:

• VSAT executable (vsat.exe)

• VSAT Client executable (vsatclient.exe)

• VSAT batch executable (vsat_batch.exe) Other modules (including VSAT server executable, VSATServer.exe) are not protected and thus do not need dongle to run. Installation of dongle drivers

The VSAT program CD includes all required dongle drivers. Occasionally, you may need to download the latest drivers. To do so, go to http://www.dsatools.com/software/sentinel/ and download the driver file (for example, “SPI 7.6.1 (Installer).zip”). To install the dongle drivers, follow these steps: (1) First be sure to remove the protection dongle from the computer. (2) Either click on the link from the installation guide on the VSAT program CD or extract the installer

from the downloaded zip and run the installer. (3) Perform a custom setup with the following options:

• Remove the “Sentinel Key Server”.

• Remove the “Sentinel Security Runtime”.

• For single-user dongles, the “Sentinel Protection Server” is not required and can be removed. This is however required for network dongles and therefore must be included in the installation.

• Ensure that both the Parallel and USB drivers are selected for installation. (4) Once installation completes, insert the dongle to the computer. For network dongles, it may take a

few seconds for windows to recognize them and to load the drivers.

http://www.dsatools.com/software/sentinel/

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(5) It is suggested to reboot the computer after installing a driver update, but this is not always necessary.

Note:

• Dongle drivers should always be installed only on the computer where the dongle is inserted. Therefore, for a computer to run the network version of VSAT, no dongle drivers need to be installed on the computer if the dongle is attached to another computer.

• If you have already installed the dongle drivers for a previous version of VSAT, there is no need to install the drivers again when you install a new version of VSAT.

• If you want to move the network dongle from one computer to another, you need to install the dongle drivers on the new computer.

• After you install a dongle driver update, you don’t need to re-install VSAT.

• After you install the network dongle drivers and insert the dongle to the computer, you can monitor the usage of the licenses by visiting port 6002 on the computer. For example, go to http://127.0.0.1:6002/ in your Web browser to monitor the license usage for a network dongle attached to your computer.

How to use single-user dongles

To use a single-user dongle, do the following:

• Install the single-user version of VSAT on your computer.

• Install the Sentinel Parallel and USB drivers on the same computer.

• Insert the dongle on the same computer.

• You can run VSAT on your computer now. How to use network dongles

To use a network dongle, do the following:

• Install the network version of VSAT on your computer.

• If dongle drivers are not installed, install them on the computer where you want to attach the network dongle. Make sure that this computer is in the same LAN as your computer.

• Ensure that the dongle is inserted on the computer where the dongle drivers are installed

• Ensure that you have license available from the dongle. See above on how to monitor the license usage for a network dongle.

• You can run VSAT on your computer now. When a network version of VSAT is started, it sends out a UDP broadcast over port 6001 to request a license from a network dongle. If the Sentinel Protection Server installed on a computer with a network dongle attached sees this broadcast, it will, if it has any available licenses, connect (over TCP port 6001 ) to VSAT that sends the broadcast and issue it a license. Be sure there is no firewall between the computer running VSAT and the computer with the dongle that is blocking port 6001 or 6002. When VSAT closes, it frees the license back to the network dongle that issues it.

http://127.0.0.1:6002/

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In this manner the network dongle can be attached to any machine on the network. In some network configuration there may be trouble because typically UDP broadcasts do not get forwarded past the local subnet. If VSAT and network dongle are located in two different subnets, then you need to create an Environment Variable to help VSAT find the network dongle as its broadcasts would go unanswered. On all VSAT computers that are outside the dongle subnet, the Environment Variable “NSP_HOST” can be set to the IP address of the computer hosting the network dongle. If VSAT sees the NSP_HOST variable, it will not broadcast to find a license, but instead directly connect to the IP specified by the NSP_HOST variable. Troubleshooting ideas

If you get a message windows indicating “Powertech SuperPro key not found…Try again?” when you run VSAT, here are a few things you can try to fix the problem:

• This message indicates that VSAT is looking for a single-user dongle. So if you intend to use a network dongle to run VSAT, install the network version of VSAT.

• Ensure that a single-user dongle provided by Powertech is inserted at the USB port of your computer.

• Ensure that the dongle drivers are installed on your computer.

• Ensure that VSAT is enabled on the dongle you use. This may be the issue if you licensed other software from Powertech and added VSAT later. Then the original dongles issued for other software will not be enabled for VSAT. If you are not sure on this, please contact Powertech for clarification.

• Occasionally, a dongle may break down after some time of use. Please contact Powertech should this happens.

If you get a message window indicating “...Network key not found...?” when you run VSAT, here are a few things you can try to fix the problem:

• This message indicates that VSAT is looking for a license from a network dongle. So if you intend to use a single-user dongle to run VSAT, install the single-user version of VSAT.

• Ensure that a network dongle provided by Powertech is inserted at the USB port of a computer in the same LAN as your computer.

• Ensure that the dongle drivers are installed on the computer where the dongle is attached.

• Ensure that there is no firewall in the network for port 6001 and 6002.

• If the computer with the network dongle attached and the computer running VSAT are in different subnet, you need to set a NSP_HOST variable as described above.

• Ensure that VSAT is enabled on the dongle you use. This may be the issue if you licensed other software from Powertech and added VSAT later. Then the original dongles issued for other software will not be enabled for VSAT. If you are not sure on this, please contact Powertech for clarification.

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• Occasionally, a dongle may break down after some time of use. Please contact Powertech should this happens.

1.4 Included Files

The “Typical” installation creates the following subdirectories and files under the program directory (e.g. VSAT):

Bin\ Program files VSAT.exe VSAT stand-alone executable VSATClient.exe VSAT client executable VSAT_batch.exe VSAT batch executable DSAOA.exe DSAOA executable CtgConverter.exe A tool to convert contingencies in PSS/E or Powerworld format to VSAT

format *.dll DLLs required by various program modules Data\ Test cases

vsat.vsa Case (Master Scenario) file with four scenarios *.snr scenario files of test cases t.* data files of test cases (powerflow file, transfer file, etc.) ref-output\ *.* reference output files of test cases Manual\ Documents

VSAT-manual.pdf VSAT manual DSAOA- manual.pdf DSAOA manual DSA_Contingency_Converter.pdf Contingency Converter user manual VSAT Release Notes.pdf A document describing the new models and features in each VSAT

release

Server\ VSATServer program and server working files

VSATServer.exe VSAT server executable (required by VSAT client)

Ems\ Auto mode working files (empty at installation)

1.5 Running VSAT Test Cases

To run the test cases:

(1) To use VSAT Client-Server, start VSAT Server from the Start menu Start | Programs |

DSATools | VSAT n.m | VSATServer (where n and n.m are version number of DSATools and VSAT release). This starts the server in Server directory and a window will open showing the server status (see Section 4.1 for details). If you have installed the server on several computers, you may start each server in the same way.

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(2) Start VSAT Client (to use with multiple servers) or VSAT stand-alone from the Start menu Start |

Programs | DSATools | VSAT n.m | VSATClient or Start | Programs | DSATools | VSAT n.m |

VSAT. This opens the VSAT main window and loads in the vsat.vsa master scenario file in Data subdirectory. If this file is not loaded, under File menu select Open and in the Open window find vsat.vsa in the Data subdirectory of VSAT and double click on it. See Section 3.2.9 for details

(3) If you started VSAT Client, under View menu in the VSAT main window (shown below), select

Servers. In the Server List window, you should see the running servers as Enabled and Free. If not, you need to add the servers as described in Section 4.1.

(4) Under Analysis menu in the VSAT main window, select Run Security Assessment (or click on

the Run button � on the tool bar). The scenarios will run and when the run is completed, the VSAT main window shows “Finished” in the Status column and displays the transfer limits. Under the Range Scenarios tab in the lower part of the VSAT window, the bar charts and limit table of scenarios 1, 2 and 4 are displayed as shown in Figure 1.1.

Figure 1.2: VSAT main window after completed run

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(5) Click on the sxy tab to see the Secure Region and limit table of scenario 3 as shown in Figure 1.3.

Click on a green dot on secure region boundary to see X and Y values at that point. Click on a colored dot outside the secure region to highlight its corresponding row in the limit table, showing its X, Y and D values and the limiting contingency and violation at this point.

(6) The following output files will be created by this run:

sx.* , sx-*.* outputs of scenario 1 (t-x.snr) sy.* , sy-*.* outputs of scenario 2 (t-y.snr) sxy.* , sxy-*.* outputs of scenario 3 (t-xy.snr) sz.* , sz-*.* outputs of scenario 4 (t-z.snr)

You may compare these files with corresponding s*.* files in the Data\Ref-output subdirectory of VSAT to ensure the program has produced correct and complete results.

(7) To run the Remedial Action Module, in the VSAT main window select the Analysis | Remedial

Action menu. This opens the RA window as shown in Figure 1.4

• In the Select Scenario pull-down list, select scenario 1 - sx.

• In the Select the Operating Point … box type 4200.

• Pull down the Run menu and select Sensitivity method. RA runs and the results are displayed

Figure 1.3: Plot and table of security limits of S35-XY scenario

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1.6 User Support Information

Powertech provides full technical support to VSAT users who subscribe to support services from Powertech. Please direct your questions or comments to Powertech Labs Inc. Attention: Dr. Lei Wang 12388 – 88th Ave Surrey, BC Canada V3W 7R7 Telephone: (604) 590-7450 Fax: (604) 590-6656 Email: [email protected] The latest news on VSAT development, program releases, and user group activities is also posted on DSAToolsTM website at www.DSATools.com.

Figure 1.4: Remedial Action window

mailto:[email protected]

http://www.dsatools.com/

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2. Overview

2.1 VSAT Description

VSAT is a state-of-the-art tool for the assessment of power system voltage security. VSAT includes a number of specialized analytical techniques designed to permit the efficient analysis of large complex power systems. With VSAT, the user can specify a large number of scenarios which will be automatically analyzed to provide such information as the critical contingencies and voltage security limits. The computations performed by VSAT are based on powerflow methods which, through many years of research and industry experience, have proven to produce practical and accurate results. In special situations in which time-domain simulations are required, such as when system dynamics and fast instability may be a concern, the companion Transient Security Assessment Tool (TSAT) can be used. Together, VSAT and TSAT provide a comprehensive assessment of all important aspects of system security. VSAT has been designed for both off-line (planning and operational planning studies) as well as on-line (connected directly to an energy management system and enabled to automatically assess voltage security using live system snapshots) use. This document describes the general features and use of the program, but is mainly focused on the off-line application.

2.2 Security Assessment Module

The Security Assessment Module determines:

• Voltage security of a given base operating point

• Security limits of one and two-dimensional power transfers (Range or Region of secure operation of the system).

The base or any other operating point (increased power transfer) is deemed Voltage Secure if it meets the specified voltage security criteria. The security criteria supported in this version of VSAT can be any combination of the following: (1) The system remains Voltage Stable (powerflow solution exists) in pre-contingency and all post-

contingency conditions (2) The system has the minimum specified margin to instability. This means the system remains

Voltage Stable if it is stressed by the specified MW/MVAr amount of margin requirement (3) Pre and post-contingency voltages are within specified limits (4) Pre and post-contingency VAr reserves of selected sources are larger than specified limits (5) Pre and post-contingency loading of lines and transformers are below the specified thermal ratings

2.2.1 Secure Range

The Secure Range (one-dimensional transfer limit) indicates how far the power transfer can be increased in a specific direction before violating the voltage security criteria. The transfer increase is specified as any combination of load and generation changes.

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For example, suppose there are two generations areas, G1 and G2, and a load area, L1, in a system (Figure 2.1). If the load is increasing, the operator may wish to know how much load increase can be supplied from G1 securely (i.e., without violating the voltage security criteria). In this case the Transfer is defined as G1 increase along with L1 increase. G1 is called the “source” and L1 is called the “sink” of this transfer. Similarly, the secure range may be computed for the transfer of power from G2 to L1. Another transfer direction can be 60% increase in G1 and 40% increase in G2 along with L1 increase. The secure range of each transfer is displayed in a bar chart as in Figure 2.2. These graphs show how far the transfer can increase until one or more contingencies cause violation of one or more security criteria. For example in this figure, G1 can supply 800 MW additional load (with G2 remaining constant), G2 can supply 600 MW additional load (with G1 constant) and G1 and G2 together (with 60/40 share) can supply 700 MW additional load before contingencies would cause insecurity.

2.2.2 Secure Region

The Secure Region indicates how far the system can be moved from the current operating point in any direction consisting of three independent sources or sinks (called two-dimensional transfer). For the above example, these can be G1, G2 and L1. In this case the secure region is displayed as in Figure 2.3 The secure region is computed in radial directions, each starting from the base point (2000, 1500 in the figure) until the secure boundary is reached where one or more contingencies cause the violation of one or more of voltage security criteria.

2.2.3 Modal Analysis

At the voltage stability limit (unsolved powerflow), Modal Analysis (Eigen analysis of the Jacobian matrix) can best identify the location of instability (the critical region of the system). The critical "Mode" computed at this point and the relative participation of buses in that mode show where in the system the

G1

2000 2800 3200

G2

1500 2100 2300

G160% + G240%

3500 4200 5300

Figure 2.2: Bar charts of 1-D Secure Ranges

2000

1500 •

G1

G2

2000

1500 •

G1

G2

Figure 2.3: Display of 2-D Secure Region

G1

L1G2

Figure 2.1: Schematic System

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instability occurs. The user can request Modal Analysis at this point or at any specified transfer level and contingency.

2.2.4 VQ Curve Computation

VQ curve computation is one of the earlier methods of voltage stability analysis. In addition to showing the sensitivity of the bus voltage to reactive power injection (or reactive load) at that bus, the curve shows the reactive power margin at that bus, which is how much the system can be stressed by reactive load increase at that one bus before it becomes “unstable”. The computation of VQ curves is very time consuming and cannot reveal system voltage stability problems. PV curve (transfer increase) computation and Modal Analysis are much more useful for determining the stability margin of the system (with respect to realistic stresses, not an artificial reactive stress at one bus alone) and identifying the weak buses and voltage collapse regions for each contingency.

2.3 Contingency Screening Module

The Contingency Screening Module screens all the specified contingencies to find the most severe ones. The severity is with respect to the Voltage Stability (VS) margin and the Thermal margin of contingencies. The specified contingencies may include all possible single element outages, double outages (of two parallel lines), or any other contingencies provided in a file. The module analyzes all these contingencies to find those with the smallest VS margin and Thermal margin. The VS margin of each contingency is the difference between the pre-contingency transfer at the initial operating point (Po) and the last point where the post-contingency solution exists (Pn). The Thermal margin of each contingency is the difference between the pre-contingency transfer at the initial operating point (Po) and the last point where the post-contingency powerflow has no thermal limit violation (Pnt). The user may request that “N” most severe contingencies be identified, or that all contingencies with VS margin or Thermal margin smaller than “X MW” (or “x%”) be identified. The user may provide an exhaustive list of all potential contingencies (the “Full List”) and designate a number of contingencies as “Must-Run” (do not screen) or “Don’t-Run” (do not analyze). The program will then include the “Must-Run” contingencies and exclude the “Don’t-Run” contingencies from the selected contingencies (regardless of their severity). For the technical approach to screen contingencies, please refer to the following paper: Vaahedi, E.; Fuchs, C.; Xu, W.; Mansour, Y.; Hamadanizadeh, H.; Morison, G.K.; “Voltage Stability Contingency Screening and Ranking”, IEEE Transactions on Power Systems, Volume 14, Issue 1, Pages 256 – 265, Feb. 1999.

2.4 Modeling of System Protection Schemes

System Protection schemes (SPS) modeling allows representation of automatic or manual (operator) control actions during pre- and post-contingency powerflow solutions. These actions include System Protection Schemes or Remedial Action Schemes (RAS) which, when a triggering condition is met, automatically or manually (by operator) apply a protection or remedial action. Triggering conditions can be such things as bus voltage, line flow, etc. Actions can be such things as line tripping, generation reduction, load shedding, etc. Each SPS can have one or more schemes, and each scheme can have one or more triggering conditions and one or more actions (in one or more stages). SPS schemes are applied in the order of their user-

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specified priority. If the triggering conditions are met for two or more schemes with the same priority, the actions of these schemes are applied at the same time.

2.5 Remedial Action Module

When an operating point is found to be insecure, the user may wish to know what is the best action to make that operating point voltage secure. The Remedial Action (RA) module finds the answer among the user-specified list of available controls, such as adjusting generator and SVC scheduled voltage, capacitor and reactor switching, ULTC tap adjustment, generation re-dispatch, and load shedding. RA first attempts to find the best Preventive control. These control actions would be taken before any contingency happens. If the identified preventive control is not sufficient to make the operating point secure for all contingencies, RA finds the necessary Corrective controls for each critical contingency. These controls (such as capacitor switching and load shedding) would be taken after the contingency happens to keep the system secure. The Sensitivity method of RA, finds the best controls based on the sensitivity of the security violation to the controls. The process in general terms is the following:

• Preventive control:

� If the operating point itself is unstable (powerflow does not solve), find the best controls to make it stable.

� Find the best controls to remove voltage limit violations (pre- or post-contingency) � Find the best controls to remove stability margin violations (pre- or post-contingency). Each

control is checked to see if it causes voltage limit violation. If it does, it will be rejected and RA will search for another control.

� Find the best controls to remove VAr reserve violations (pre- or post-contingency). Each

control is checked to see if it causes voltage limit or stability margin violation. If it does, it will be rejected and RA will search for another control.

• Corrective control:

� If the identified preventive controls are not sufficient to remove all violations, examine each contingency individually and find the best controls to remove its violations, similar to the preventive control process above.

2.6 Distributed Processing

To be able to quickly analyze very large system models, large number of scenarios, and/or contingencies, VSAT has a distributed processing (client/server) version, as well as a stand-alone version. In the distributed processing version, one machine (which must be a PC) is used as client and several machines (not necessarily PCs) on the network are used as servers. The VSAT client automatically detects available servers running on the network and distributes the computation tasks to those servers. There is no limit on the number of servers used, and the computation speed increases almost linearly with the number of servers (depending on the relative power of the servers and required computations). The required setup for distributed processing is described in Chapter 6.

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2.7 Scenarios and Data Files

This section describes the basic input and output file structures of VSAT and outlines the Scenario concept. Input data and general solution and control parameters required by VSAT are provided through Data

Files. Collection of data files for computing one scenario (e.g., one transfer limit computation) is specified in a Scenario File (described below) and collection of Scenario Files for one VSAT run is specified in a Case File (or Master Scenario File). VSAT displays the results of the simulations in tables and graphs. In addition, a number of Output Files are created which can be used to further analyze the results.

2.7.1 The Scenario Concept

VSAT runs consist of the analysis of user specified “scenarios” which define the system conditions and types of analysis to be performed. A scenario includes the following type of information:

• A solved powerflow representing the base case conditions.

• Specification of the contingencies to be analyzed.

• Defined security criteria in terms of allowable voltage range, maximum allowable voltage declines, minimum allowable reactive reserves, and minimum allowable margin to voltage instability.

• Specification of one transfer (which defines how load and generation are to be changed), if a transfer limit computation is requested.

• Variables to be monitored during analysis.

• Computation solution parameters and other data as needed (such as governor response, AGC, etc).

• Available Controls and parameters for Remedial Action computation, if requested.

• Definition of System Protection Schemes, if requested. The above information is provided by the user in a set of data files, e.g., powerflow file, transfer file, etc. The names of the data files for each scenario are specified in the Scenario File. The user may setup any number of Scenarios and specify a collection of scenarios in a Master Scenario File. VSAT can analyze all scenarios of a Master Scenario File (also referred to as a “VSAT case”) automatically in one execution cycle. Scenarios may share data files, for example, two scenarios could use the same base case powerflow, but examine different sets of contingencies or transfers. Scenario Files and Master Scenario Files can be set up through the VSAT GUI or separately by using any text file editor.

2.7.2 Data Files

Data files for each scenario, depending on the type of analysis to be run, may include the following:

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Primary Data Files

• Base Powerflow File: Contains the base case powerflow data in PFB format. Data in other formats (IEEE, PTI, PECO, BPA, EPRI, PSF ASCII) must be converted into PFB format as described in Sections 3.1.1 and 3.3.

• Parameter File: Contains parameters that specify program control actions, solution parameters, and output options.

• Transfer File: Contains specification of Transfer in terms of load and generation increase/decrease.

• Criteria File: Contains the voltage and reactive reserve criteria.

• Margin File: Contains the specification of the margin that is part of the voltage stability criteria.

• Full-Set Contingency File: Contains the full list of contingencies to be passed to contingency screening.

• (Screened) Contingency File: Contains the list of contingencies to be used in the security computation. If contingency screening is to be performed on the Full-Set Contingency list, this file will contain the list of contingencies identified by the screening. If contingency screening is not to be performed, this file contains a list of contingencies provided by the user.

• Contingency Screening Parameter File: Contains parameters for screening the contingencies.

• Monitor File: Contains the specification of the parameters to be monitored during the transfer limit computation.

• Interface and Circuit File: Contains description of interfaces and circuits to be monitored.

Secondary Data Files

• Contingency Script File: Contains the script (description) of contingency groups. Actual contingencies can be created from this script.

• Generator Capability File: Contains parameters for computing generator VAR limits based on field and armature current limits.

• Generator Coupling File: Contains combined cycle power plant data.

• Governor Response File: Contains governor data used in computing MW generations according to governor responses.

• AGC Action File: Contains AGC data used in computing MW generations according to AGC action.

• Load Conversion File: Contains description of voltage dependent load models to be used.

• Load Swap File: Contains the bus-pairs for swapping the load if the first bus is outaged.

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• Branch Rating File: Contains ratings of specified lines and transformers to be used in limit checking.

• Modal Analysis Parameter File: Contains parameters for Modal Analysis of unstable cases.

• VQ Curve File: Contains data (bus number, etc.) for computation of VQ curves.

• Control Mode File: Contains mode (locked, manual, etc.) of control devices (tap changers, etc.).

• SPS File: Contains System Protection Scheme (or Remedial Action Scheme) data.

Remedial Action Data Files

• Remedial Action Control File: Contains information pertaining to the availability and priority of the voltage control devices such as shunts, generator scheduled voltage, etc. for the remedial action module.

• Remedial Action Sensitivity Method Parameter File: Contains parameters for the Remedial Action computation using the sensitivity method.

These data files, with the exception of the powerflow file, are ASCII text files and can be set up through the VSAT GUI or separately by using any text file editor. The relationships of the input files used by VSAT are shown in Figure 2.5. Figure 2.6 shows the VSAT output files. The use of these files and their formats and contents, are described in various parts of this manual. The data files and scenario files of test cases are installed in the Data subdirectory of VSAT. You may inspect the contents of these files and use them as examples to set up your own data files.

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MASTER

SCENARIO

FILE 1 (.VSA)Scenario File 1

Scenario File 5

MASTER

SCENARIO

FILE 1 (.VSA)Scenario File 1

Scenario File 5

Master Scenario Files-Contain Lists of Scenario Files

Scenario Files-Contain Lists of Data Files

Powerflow

Files (.PSF or .PFB)

Parameter

Files (.PRM)

Transfer

Files (.TRF)

(Screened) Contingency

Files (.CTG)

Margin

Files (.MRG)

Full-Set Contingency

Files (.CTF)

Criteria

Files (.CRT)

Contg. Screen. Parameter

Files (.PCA)

Monitored Variable

Files (.MON)

Interface and Circuit

Files (.ITF)

MASTER

SCENARIO

FILE 2Scenario File 2

Scenario File 5

Scenario File 3

Scenario File 4

MASTER

SCENARIO

FILE 2Scenario File 2

Scenario File 5

Scenario File 3

Scenario File 4

MASTER

SCENARIO

FILE NScenario File 4

Scenario File 6

Scenario File 8

Scenario File 9

MASTER

SCENARIO

FILE NScenario File 4

Scenario File 6

Scenario File 8

Scenario File 9

SCENARIO

FILE 1 (.SNR)Powerflow File A

Parameter File C

Transfer File B

Other Data Files

SCENARIO

FILE 1 (.SNR)Powerflow File A

Parameter File C

Transfer File B

Other Data Files

SCENARIO

FILE 2Powerflow File D

Parameter File C

Transfer File A

Other Data Files

SCENARIO


Parameter File C

Transfer File A

Other Data Files

SCENARIO


Parameter File B

Transfer File A

Other Data Files

SCENARIO


Parameter File B

Transfer File A

Other Data Files

Remedial Control

Files (.RMC)

Data Files-Contain System and Control Data

Contingency Script

Files (.CTS)

Sensitivity Parameter

Files (.SPR)

Generator Capability

Files (.GCC)

Generator Coupling

Files (.CCP)

Governor Response

Files (.GVR)

AGC Action

Files (.AGC)

Load Conversion

Files (.CLD)

Load Swap

Files (.LSW)

Branch Rating

Files (.RAT)

Model Analysis Parameter

Files (.MDP)

VQ Curve

Files (.VQC)

SPS

Files (.SPS)

Control Mode

Files (.CMF)

INPUT

VSAT

Remedial Action Data Files

Primary Data Files Secondary Data Files

Figure 2.4: VSAT input files

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V S A T

O UTPUT

Remedial Action Detail Control Report

Scenario - id - ras . dtc



Remedial Action Main Output

Scenario - id . ras


Scenario - id . ras

Remedial Action Summary Report

Scenario - id - ras .rpt



User Requested Reports

Scenario - id - xxx. rpt



Contingency Screening Report

Scenario - id . cao


Scenario - id . cao

SPS Actions Report

Scenario - id - sps .rpt

SPS Actions Report


Main Output Report

Scenario - id . prg

Main Output Report

Scenario - id . prg

Monitored Variable Tables

Scenario - id . pvt


Scenario - id . pvt

PV Curve Output

Scenario - id . pvp

PV Curve Output

Scenario - id . pvp

Security Limit

Scenario - id . lmt

Security Limit

Scenario - id . lmt

VQ Curve O utput

Scenario - id . vqp

VQ Curve O utput

Scenario - id . vqp

V S A T

O UTPUT






Scenario - id . ras


Scenario - id . ras










Scenario - id . ras


Scenario - id . ras










Scenario - id . cao


Scenario - id . cao

SPS Actions Report


SPS Actions Report







Scenario - id . cao


Scenario - id . cao

SPS Actions Report


SPS Actions Report


Main Output Report

Scenario - id . prg

Main Output Report

Scenario - id . prg


Scenario - id . pvt


Scenario - id . pvt

PV Curve Output

Scenario - id . pvp

PV Curve Output

Scenario - id . pvp

Security Limit

Scenario - id . lmt

Security Limit

Scenario - id . lmt

VQ Curve O utput

Scenario - id . vqp

VQ Curve O utput

Scenario - id . vqp

Main Output Report

Scenario - id . prg

Main Output Report

Scenario - id . prg


Scenario - id . pvt


Scenario - id . pvt

PV Curve Output

Scenario - id . pvp

PV Curve Output

Scenario - id . pvp

Security Limit

Scenario - id . lmt

Security Limit

Scenario - id . lmt

VQ Curve O utput

Scenario - id . vqp

VQ Curve O utput

Scenario - id . vqp


Scenario - id . cao


Scenario - id . cao


Scenario - id . cao

Trf/Ctg Transfer/Contingency

Details Scenario - id . dsa

Figure 2.5: VSAT output files

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2.8 Computation Process

This section describes the overall process of analyzing the security of each Scenario. Step 1: The Scenario File and subsequently all related data files specified in the scenario file are read in. Multiple Scenario Files can be read in at one time by specifying a Master Scenario File. If the powerflow data is not in PFB (or PSF which is an older version of PFB format) format, it must be converted to PFB before any computation (manually or through the Auto feature). Step 2: The contingency list in the Full-Set Contingency File is created from the Contingency Script File, or prepared manually, and then screened to identify the critical contingencies for each scenario. This process, if needed, must be initiated manually (it can also be triggered automatically by the Auto feature for each analysis cycle). The number of contingencies to be selected and other parameters used for screening are provided in the Contingency Screening Parameter File. The results of the screening (the critical contingencies) are written to the (Screened) Contingency File for use in the Security Assessment, and displayed in the Contingency Screening window. See the next section for details of screening process. This step can be bypassed if the user has provided all the contingencies (prepared manually or created from the Contingency Script file) for the security assessment step and does not wish to shorten the contingency list by screening. Contingencies defined in the third party formats (e.g. Siemens/PTI PSSE or PowerWorld Auxiliary files) can also be converted (imported) by VSAT “Contingency Converter” utility. Step 3: The Security Assessment is performed for the base point (current operating point) provided in the Powerflow File. The Parameter File is used to specify the computation options, control options and parameters for the powerflow solution, and the level of output reporting. Security assessment solves the powerflow for the base case (pre-contingency) and for each of the contingencies in the Contingency File. If for a pre or post-contingency case the powerflow does not converge, that case is considered Voltage Unstable. Each successful powerflow solution is checked for violations of the security criteria, including voltage and reactive reserve limits defined in the Criteria

File and thermal limits for branches specified in the Parameter file or Rating File. If a Margin File is specified, the base point is then stressed by the specified amount of required margin and pre and post-contingency cases are solved at that stress level. If a case does not solve (powerflow does not converge), it is considered to have insufficient Stability Margin.

In case of instability, security criteria violation, or insufficient margin in pre or post-contingency, the base point is deemed Insecure.

If Modal Analysis is requested in the Parameter File (with or without the optional Modal Analysis

Parameter File) for the pre-contingency or one of the contingencies in the base point (before or after stress), after the specified case is solved, Modal Analysis is performed for that case (and VSAT run

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terminates). Modal Analysis consists of computing the Jacobian matrix (and reducing it to the V-Q sub-matrix) and computing a specified number of its smallest eigenvalues and associated eigenvectors.

If VQ curve computation is requested, the curves are computed at requested buses after the pre- and post-contingency powerflow solutions. To compute the VQ curve at a bus, an open-VAr generator is added to the bus to vary its voltage by a specified step size within a specified range. At each voltage step the powerflow is resolved to find the required VAr injection from the generator to hold that voltage. The plot of VAr injections versus the bus voltage represents the VQ curve. VQ curves are not computed if a Margin File is specified. During powerflow solutions, special modeling can be used if the appropriate files are provided and proper flags are set in the Parameter File. These include:

• Generator Capability File: Allows modeling of generator capability curves during all powerflow solutions.

• Load Conversion File: Allows modeling of voltage dependent loads during post-contingency powerflow solutions. It may also be taken into account in the pre-contingency solution if loads

are defined as voltage dependent in the imported powerflow (e.g. imported from Siemens/PTI

PSSE format)

• Governor Response File: Allows modeling of governor response to load-generation mismatch caused by contingencies.

• AGC Action File: Allows modeling of the AGC action to maintain area interchanges following

contingencies.

• SPS File: Allows representation of System Protection Schemes (or Remedial Action Schemes) to apply automatic or manual protection (control) actions when specific triggering conditions are met.

Step 4: If Transfer Limit computation is requested by setting the Transfer Analysis flag in the Parameter File and providing the Transfer File, VSAT computes the Secure Range or Region of the transfer. For this, the operating point is moved with a specified step size in the direction of the Transfer until the security limit is reached. The Transfer File specifies what changes to generation and load are required to make the desired transfer. Optional Generator Coupling File may be used for performing specific mode of generation dispatch. At each step, VSAT analyses all critical contingencies, determines if any criteria violations exist, and writes the output to the appropriate files, similar to Step 3. If any criteria violations occur, VSAT deems that operating point (transfer level) insecure. The value of the transfer at the last secure point is reported as the transfer security limit.

This process may stop before finding the security limit if the transfer target value (user-specified maximum increase or decrease in the transfer) is reached, or the available dispatchable resources are exhausted (dispatched generation or load reached its maximum or minimum).

When voltage instability is encountered (either before or after the Stress), if Modal Analysis at the stability limit is requested, it is performed at the last stable case corresponding to the unstable case. For example, if contingency X causes instability at transfer step 12 after the Stress, VSAT returns to transfer step 11, applies the Stress and contingency X, and performs Modal Analysis on this case. After

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performing the Modal Analysis, VSAT may continue the analysis depends on the transfer and contingency analysis options selected in the parameter file.

If VQ curve computation is requested, during transfer increase (at every step or every nth step) VQ curves are computed for specified buses in pre- and/or post-contingency. VQ curves are not computed if Margin File is specified.

Each one-dimensional transfer limit is displayed by a bar chart in the VSAT main window. During the transfer limit computation, the secure value of the transfer is displayed as a growing green section of the bar chart. When the insecure point is reached, the remaining portion of the bar chart is shown as red and the security violation is indicated in the table beside the charts. This provides the user with a quick indication of the security limits for each transfer. In addition, the value of transfer limit is displayed in the Limit column of the top portion of the VSAT main window.

After each powerflow solution, the variables specified in the Monitor File are recorded. In addition to these being plotted in the Plots window, the following text output is created:

• Main output file: Contains descriptions of data and pre and post contingency powerflow solutions

• Monitored Variable Tables File: Contains tables of all variables specified in the Monitor File

• Voltage and VAr Reserve Violations Report\

• Overloads Report: if ratings are provided in the powerflow or the Branch Rating File and the overload check flag is set in the Parameter File

• Modal Analysis Report: if Modal Analysis is requested in the Parameter File

• VQ Plots: if VQ curves were requested in the Parameter File and Margin File is not specified.

• User Requested Reports: reports of generation, losses, etc., if requested by setting the corresponding flags in the parameter file

• Security Limit Summary Report

VSAT repeats the above process for all scenarios. If more than one server is available, the scenarios will be distributed to the servers and will be computed in parallel.

In the case of a two-dimensional transfer, the Secure Region is computed by a similar process except that VSAT traces the boundary of the secure region (separating secure operating points from insecure operating points) rather than finding a single transfer security limit. The secure region is shown in the VSAT main window as a green area on an XY plot with each axis representing one source/sink of the transfer. The boundary points of the secure region and the violation beyond each point are shown in the table beside the XY plot. Step 5: If it is desired to find the Remedial Actions for removing the security violations of an insecure operating point, the RA module of VSAT is run operating point (by the value of the source of transfer at that point) and provides the Remedial. For this computation, the user specifies the insecure Control File and optional Sensitivity Parameter File. The RA module finds the most effective controls (Preventive and, if

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needed, Corrective) to make the specified operating point secure. The selected controls are displayed in the RA window and reported in the output file. The pre-contingency case at the selected operating point must be Voltage Stable for RA to try to resolve other pre or post-contingency security violations.

2.8.1 Contingency Screening Process

In general, out of a large number of possible contingencies, only a few contingencies will be critical to voltage stability and thermal security. The contingency screening feature in VSAT is designed to identify these critical contingencies. The screening does not use any approximation (linearization or extrapolation) and accurately classifies the contingencies based on their exact Voltage Stability (VS) margin and Thermal margin. The general process for finding Nc most severe contingencies among the full list of contingencies is the following: (1) Starting from the initial point (Po), compute only the pre-contingency PV curve, in the direction of

the Transfer, to find its nose point (Pm).

(2) Reduce the transfer from the nose point by s1% (or S1 MW). Call this point P1.

(3) Solve all the contingencies at P1 and find N1 contingencies that do not solve or that have thermal limit violations.

(4) If N1 = Nc, stop.

(5) Set the counter i to 1.

(6) If Ni > Nc, reduce the transfer to Pi+1 = (Po + Pi) / 2, and find Ni+1 contingencies, among the Ni insecure contingencies identified at Pi. Else, increase the transfer to Pi+1 = (Pi + Pm) / 2, and find Ni+1 contingencies among all the contingencies that are insecure (do not solve or have thermal limit violations) at this point (these include the Ni contingencies identified at Pi which do not need to be resolved).

(7) If Ni+1 = Nc, stop.

(8) If Ni > Nc, replace Pm by Pi , else, replace Po by Pi, increase the counter i by 1, and go to step 6. The process stops if the search step (Pi+1 - Pi) becomes smaller than a limit, or number of search points (i) exceeds a limit. For example if the full list has 100 contingencies whose voltage stability margins are almost the same, searching for 10 severe contingencies among these 100 would reach a very small search step and too many steps, making the distinction among contingencies meaningless (because of numerical inaccuracies). VSAT has default values for the screening parameters, but for better performance the user may need to specify non-default values for some parameters (especially S1) in the Contingency Screening Parameter file. The screening parameters are:

(1) Number of contingencies to be selected for Security Assessment, Nc (2) First step size for screening, S1, in MW or in percentage (3) Minimum step size for screening (limit on Pi+1 - Pi), in MW (4) Maximum number of search points (limit on i) (5) Initial step size for searching for the nose of pre-contingency PV curve, in MW (6) Cut off step size for searching for the nose of pre-contingency PV curve, in MW

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To find Nc severe contingencies, all contingencies will be solved at the first step of screening and depending on the number of insecure contingencies at this point, N1, compared to Nc, some or all contingencies will be solved at the next points. For fast computations, one must ensure that N1 is close but larger than Nc. An alternative to the above process is to ask for selection of all contingencies with VS margin or Thermal margin less than X MW (or x%). In this case, the pre-contingency PV curve is computed up to X MW (or x%) margin and all contingencies are solved at this point. The unsolved contingencies have VS margin less than X. The contingencies that cause thermal limit violations have Thermal margin less than X. This is equivalent to the computation in the first step of screening in the previous process. For the second option, instead of parameters a), c) and d) above, the following parameter is specified: (7) Select contingencies within margin X MW (or x%) In the second option, parameter b) is ignored, unless the pre-contingency itself has less than X MW margin. In this case, contingencies with margin less than “Pre-contingency Margin” minus “First step size” are selected. The user may designate a number of contingencies as “Must-Run” or “Don’t-Run”. The program will then include the “Must-Run” contingencies and exclude the “Don’t-Run” contingencies from the selected contingencies (regardless of their severity).

2.9 VSAT Structure

There are two versions of VSAT installation: (1) Stand-alone: in which the Graphical User Interface (GUI) and computation engines for

Contingency Screening, Security Assessment and Remedial Action computation are all integrated into one program. This version does not offer the distributed processing feature.

(2) Client-Server: in which the GUI is provided by the client and the computation engines are included

in the server. The client does not perform any computation itself. Instead, it distributes the computation tasks to one or more servers that are running on the same computer or other computers on the network. The servers send the result of the computations back to the client for viewing/plotting.

The servers cannot be used independently without the client and the user interacts only with the client (except of course for starting and stopping the server on each computer). The client automatically detects and connects to all running servers on the network and, transparent to the user, distributes the scenarios and contingencies (when there is only one scenario left to compute) to the servers. You may use either version depending on your computational environment, workload and performance requirements. The client-server version is suitable for heavy computations on dedicated computers, and the stand-alone version is suitable in a multi-user setting where one person should not use up the processing power of other users’ computers.

2.9.1 VSAT Main Window

The Graphical User Interface (GUI), provided by the VSAT client and VSAT stand-alone programs, is used for setting up scenarios, initiating and controlling the computations, and viewing the results. These

VSAT Users Manual



activities are described in the following sections of this manual. The VSAT main window as shown in Figure 2.7 (after running a number of scenarios) provides: (1) Summary of scenarios and their results (2) Graphical display of computed security limits (3) Tables of insecurities and limits (4) Computation progress and error messages (5) Pull-down menus and toolbar buttons for:

• Opening and saving the Master Scenario (case) file

• Scenario setup and data viewing and editing

• Running Contingency Screening

• Running Security Assessment, pausing the run, stopping the run

• Viewing and plotting the results

• Remedial Action computation

• Controlling servers (in Client-Server version)

• Viewing this manual on line and Help

You may resize the sections and columns of the main window by clicking on the lines that separate them and dragging them to right/left or up/down.

Figure 2.6: VSAT main window

Secure Region Plot and Limit Table for Two-Dimensional

Summary of Scenarios

Table of Insecurities Bar Charts of Transfer Limits

Tabs to View Run Messages of Scenarios

Resize

Resize

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3. Setting Up Scenarios

The Scenario File and its data files may be set up manually (created by a text file editor) and then loaded in VSAT, or they may be set up using the VSAT GUI.

3.1 Preparing the Scenarios Manually

3.1.1 Preparing the Data Files

The powerflow data must be provided in the binary PFB or PSF file. This data can be created from a Powerflow file in PTI Rawd, GE EPC or other formats by performing a conversion in VSAT. The other data files (e.g. Parameter File, Contingency File, etc.) are ASCII text files. The format and function of these files are described in Chapter 8. You may create these files by using the data editor built in VSAT or any text editor.

3.1.2 Preparing the Scenario File

Each Scenario File contains the name of all necessary data files for running one VSAT scenario. Data file names may be used in more than one Scenario File thereby allowing the mixing and matching of data files to create different scenarios. The first line of each Scenario File must contain: [VSAT X.Y Scenario] The optional scenario description, which may consist of several lines of text to describe the scenario, must be preceded by the following record: {Description}

And they must be followed by: {End description} Each data filename must be specified on one record which contains an identifier, the "=" sign, and the file name enclosed in single quotes as in the following: Identifier = ‘file name' Where the Identifier is one of the following: Powerflow File PFB File Parameter File Transfer File Criteria File Margin File Contingency Script File Full-Set Contingency File

VSAT Users Manual



Contingency File Contingency Screening Parameter File Monitored Variable File Interface and Circuit File Generator Capability File Generator Coupling File Governor Response File AGC Action File Load Conversion File Load Swap File Branch Rating File Modal Analysis Parameter File VQ Curve File Control Mode file SPS file RA files: Remedial Control File Sensitivity Parameter File The data file names in the Scenario File can appear in any order and only the PFB File (powerflow binary data) and those files that are needed for the computations (depending on the computation options and features specified by the user) need to be specified. There can be an optional End record in the Scenario File as: [END] The program ignores any record starting with "/", blank records, and any record after the End record. The Identifiers are case insensitive and can be preceded and followed by any number of blank spaces. However, their spelling (including spaces between words) is fixed. Tabs must NOT be used as white space (instead of blank space). The file names may specify the absolute or relative path of the file location, e.g. 'c:\vsat\data files\test.ctg' or '..\case5\t1.trf'. Note that in Security Assessment, contingencies are read from the Contingency file and the Full-Set Contingency file is ignored. In Contingency Screening, the full-set contingencies are read from the Full-Set Contingency file and after the top N critical contingencies are found, they are written into the Contingency file.

3.1.3 Preparing the Master Scenario File

Once a number of Scenario Files have been prepared, their filenames can be specified in a Master

Scenario (or Case) File. In this way, the user needs only to provide VSAT with the name of Master Scenario File and all the scenarios in that file will be loaded in. Any number of Master Scenario Files can be kept by the user, each with its own unique combination of scenarios.

The format of the Master Scenario File is as follows: Scenario1_ID, 'Scenario1_Filename' Scenario2_ID, 'Scenario2_Filename'

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Figure 3.1: A blank VSAT main window

Scenario3_ID, 'Scenario3_Filename' Scenario4_ID, 'Scenario4_Filename'

The Scenario_ID is used to identify the scenarios in the GUI and to name the output files as described in Chapter 7.

3.2 Preparing the Scenarios through VSAT GUI

3.2.1 Creating a New Scenario

The fastest way of creating a new scenario is to open (Add) an existing scenario (one of your previous scenarios or a test scenario file provided with VSAT), modify it, and save it as a new scenario as described in the next sections. However, you may create a new scenario from scratch as follows. (1) Start VSAT Client or Stand-alone. If there is a Master Scenario File called vsat.vsa in the

“Starting” directory, it will be loaded in and the window will show the scenarios in that file. In that case, you may use File | New menu to get a blank VSAT window. See Figure 3.1

(2) In the VSAT main window, pull down the Scenario menu and select New, as shown in Figure 3.2

Figure 3.2: Creating new scenario

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Figure 3.4 Specifying data files for the new scenario

Figure 3.3: Specifying Scenario File

(3) The Scenario File specification window appears where you can navigate to (Look in) different directories, specify a File name for the new scenario file and click the Open button. See Figure 3.3. Note that if you specify an existing scenario file, that scenario will be opened instead of creating a new scenario.

(4) The Scenario window opens (as shown in Figure 3.4), showing the new scenario, which has no

other data file. You need then to click on each data in the list in the left side to specify the required data in the right side. For example, after you click on Parameter, you may either open an existing Parameter file, or specify the required parameters in the right side and save them in a new Parameter file, which will be included in the scenario. See the next section for details on how to open, modify and save the data files.

(5) Close the Scenario window (Click Yes in the prompt for saving the changes) to return to VSAT

main window.

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Figure 3.7: Adding a

scenario

Figure 3.6: Changing Scenario ID

3.2.2 Adding Existing Scenario Files

If you have existing Scenario Files which were created during a previous session, or which were created manually, you can add them to the existing set of loaded scenarios. In the VSAT main window, pull down the Scenario menu and select Add (Figure 3.7). The file Open window will pop up where you can find and open (load in) a saved Scenario file. See Figure 3.5.

You may load in several scenarios (create new ones or open existing ones). VSAT assigns a sequential number to each scenario and an ID ("Untitled n", where n is a number) to opened scenarios. You may change the ID of any scenario by double clicking on the ID column in the top part of VSAT main window and typing a new value. See Figure 3.6

Figure 3.5: Specifying an existing Scenario file

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Figure 3.8: Modifying a scenario

3.2.3 Modifying Scenarios and Data Files

After an existing scenario has been loaded or a new one has been created, you can view its details, replace its data files with new files, save it as a new scenario, and change the contents of its data files (remember that Scenario is a collection of data files, and each data file contains a specific data, e.g. Transfer, Criteria, etc.). To view and modify a scenario, select it by clicking on its row in the top part of VSAT main window, pull down the Scenario menu, and select Setup. You may also right click on the scenario row to get the pop-up menu where you can select Setup or just double click on the scenario row (anywhere except the ID column). See Figure 3.8. The Scenario window will appear, with the list of data types on the left section and display of the names and contents of data files on the right section of the window.

The two sections of the Scenario window can be resized by clicking on their border line and dragging it to the left or right. The icon beside each data file in the left section indicates the following:

• A blank-page symbol indicates the absence of the data in the scenario (the scenario does not include the corresponding data file).

• A text-page symbol indicates the presence of the data in the scenario.

• Multiple text-pages symbol indicates that the corresponding data file is shared by more than one scenario. If you make changes to this data, and you do not want the changes to apply to all scenarios, save the data as a new file (the other scenarios will use the old file).

• An exclamation mark in a blank-page symbol indicates that the data is specified in the scenario but the specified data file is not found (for example it might have been moved to another directory).

• A pencil on the text-page symbol indicates that the data has been changed but not saved yet.

Click on Scenario on top of the list in the left section of the Scenario window. The right section will show the scenario filename and description as shown in Figure 3.9. Click in the Description box on the right and use the Edit menu and commands similar to a text editor to change or retype the description.

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Figure 3.10: File menu of Scenario window

To view and modify a data file (e.g. the Parameter data) in this scenario, click on the corresponding name (e.g. Parameter) in the data list in the left section of the Scenario window. You will see the data filename and its contents in the right section of the window. To replace the displayed data file in the scenario by another file, click on the browse button on the right of the Filename box. This opens the Select File window, where you can select another file (with similar contents) and open it. For most data files, the data items are displayed in dialog boxes and tables with titles and labels directly related to the file format described in Chapter 8. Refer to the description of each file in Chapter 8 and description of the dialog boxes and windows in Help for the meaning and purpose of each item in these dialogs. For some of the data files, the whole content is displayed in a single text box where it can be edited as in any text file editor. The Edit menu provides common editing commands such as Cut, Copy, Paste and Find. If you click the right mouse button while in the File Contents box, a pop-up menu will provide similar commands as the Edit menu. For the format of these data files refer to Chapter 8. You may save any data (after some changes) in its current file or a new file by choosing Save or Save As from the File menu (see Figure 3.10). To save all changed data types at once in their current files, choose Save All from the File menu.

To remove a data from the scenario, select it from the list on the left (to display it on the right) and choose Remove from the File menu. If you change any of the Filenames (by opening another file to replace an existing file, or saving the data as another file) or scenario description, you must save them in the existing scenario file or a new one by choosing Save Scenario or Save Scenario As from the File menu.

Figure 3.9: Scenario window shows Scenario filename and

description

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Figure 3.11: Removing scenario

To close the Scenario window and return to VSAT main window, choose Exit from the File menu. If you try to exit the Scenario window without saving the modified data, you will be asked to confirm to save the changes, ignore the changes or cancel the command (stay in the current window).

3.2.4 Removing Scenarios

If you wish to remove a loaded scenario, select it by clicking on its row in the top part of VSAT main window, pull down the Scenario menu, and select Remove. You may also right click on the scenario row to get the pop-up menu where you can select Remove. See Figure 3.11.

3.2.5 Viewing Powerflow Data

If you wish to examine the powerflow data of a scenario, select it by clicking on its row in the top part of VSAT main window, pull down the Scenario menu, and select Open in PSAT. This opens the binary powerflow data in PSAT program where you can view buses, generators, loads, etc. (see the manual of PSAT for details). Note that if you change the data in PSAT and save it in a different PFB file, the scenario will still use the original PFB file. See section 3.3 for viewing and saving the powerflow data in the Scenario window.

3.2.6 Compare Scenarios

To compare scenarios, select it by clicking on its row in the top part of VSAT main window, pull down the Scenario menu, and select Compare Scenarios. You may also right click on the scenario row to get the pop-up menu where you can select Compare Scenarios.

3.2.7 Archiving Scenarios

To archive a scenario, select it by clicking on its row in the top part of VSAT main window, pull down the Scenario menu, and select Archive. You may also right click on the scenario row to get the pop-up menu where you can select Archive. This creates a Zip file of the scenario with all its data files.

3.2.8 Creating and Saving a Master Scenario (or Case) FILE

Once the Scenario Files have been created, the collection of scenarios and their IDs shown in the top part of VSAT main window can be saved in one Master Scenario File (or Case File). From the VSAT main

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window, pull down the File menu and select Save (if you wish to overwrite the existing Master Scenario File) or Save As (if you wish to create a new Master Scenario File). See Figure 3.12.

Any number of Master Scenario Files can be created and saved allowing the user to mix and match a set of scenarios to create a wide number of different execution runs. Only one Master Scenario File can be loaded into VSAT at a time.

3.2.9 Adding Scenarios Using a Master Scenario File

If you have previously prepared a Master Scenario File (either manually or using the GUI to create and save it) you can open that file by pulling down the File menu in the VSAT main window and selecting Open. The File Open window will popup where you can select and Open the desired file. Once opened, all the scenarios in the selected Master Scenario File will be loaded and will appear in the VSAT main window. The scenarios can then be viewed and modified, if needed, in the Scenario window as described before.

3.2.10 Archiving All Scenarios

To archive all scenarios, pull down the File menu, and select Archive Case. This creates a Zip file of all the scenarios with all their data files.

3.2.11 Exiting VSAT

To exit (close) VSAT, pull down the File menu in the VSAT main window and select Exit. If you have not saved the Master Scenario File (as described above) after adding or removing scenarios or changing their IDs, VSAT will ask you to confirm to save the changes in the current Master Scenario File, ignore the changes or cancel the command (stay in the current window).

3.3 Powerflow Data and Conversion to PFB

After you select a scenario in the VSAT main window and click on Setup to go to the Scenario window (as described in Section 3.2.3), if you click on Powerflow on the left side, the right side of the window shows the Powerflow as well as PFB or PSF filename (See Figure 3.13). If the base PowerFlow data for the scenario is provided in the PFB or PSF file (e.g., a PFB file created by any DSATools

TM program), the Powerflow file is not required. Otherwise, the Powerflow file must be specified and converted to PFB

Figure 3.12: File menu for saving

and opening Master Scenario files

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file before Contingency Screening Security Assessment or any other computation. Also, if you change the Powerflow file or its contents, you must re-convert it to PFB before any computation.

To specify/change the files, click on the browse button on the right of Powerflow Filename or PFB or

PSF Filename box to open the Select File window. In this window, find the desired file and click the Open button. If the PFB file does not exist (it needs to be created for the first time) you can enter a new name in the File Name box of the Select File window and click the Open button. To convert the Powerflow file to PFB file, first specify its format by selecting an item in the Powerflow

Format pull-down list, then click on the Convert to PFB button. The conversion will start and a message window will appear, showing the progress and possible error and warning messages. It also possible to convert a powerflow data file and solve powerflow before saving it in the PFB (or PSF) format. As seen

in Figure 3.13, Solution Method shown is by default is “No Solution”.

You can examine and even modify the PFB data by clicking on the Open PFB in PSAT button. This starts the PSAT program, where you can examine data of buses, generators, loads, etc., modify the data if needed and save the PFB file (see the manual of PSAT for details). If in PSAT you save the data in a different PFB file, the scenario will use the new file.

3.4 Data Views

As described in Section 3.2.3, when you double click on a scenario in the VSAT main window, the Scenario window appears, showing the list of all data files (data tree) in the left side. By clicking on each data in this list, the right side of the Scenario window shows the filename and its contents for that data. For each data, the titles, labels, headings and contents of dialog boxes and tables in the right side of the Scenario window are directly related to the format of that data file as described in Chapter 8. Refer to Chapter 8 and description of the dialog boxes and windows in Help for the meaning and purpose of each data item in these dialogs. The following describes the general and specific aspects of data views.

3.4.1 General Features of Data Views

Every data in the data tree (e.g., Criteria) is read from and save to a data file. The name of this file is displayed in the File name box in each data view. To replace a data file by another file, click the Browse

button beside the File name box to open the Select file dialog and choose the other file to Open. The data view will show the contents of the selected data file. To save the data in the same file (after you change some of the data items) or in another file, use the Save or Save As commands of the File menu. Opening another data file or saving the data to another file (a file other than the current one in the scenario)

Figure 3.13: Converting powerflow data to PFB

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Figure 3.14: Example of data view

changes the previous filename to the new filename in the scenario. To keep the new file in the scenario, use the Save Scenario or Save Scenario As commands of the File menu.

Most data files (e.g., Criteria), as described in Chapter 8, consist of singular data items (e.g., Name of criteria data) and groups of data records (e.g., Voltage Limit groups). The composition of each group (i.e., buses, generators or loads belonging to the group) is specified by including and/or excluding areas, zones, buses, etc. It is possible to search different power system components with the specified powerflow data file when

preparing different input data files. For example, when defining buses to be monitored, the user has

access to the list of buses in the specified powerflow. The user can then pick the bus of

interest from the bus list by selecting this icon. For example, In Figure 3.14, user has access

to the list of areas and zones.

Each singular data item is displayed in a dialog box with a label the same as the item’s name in the data file. The Description dialog box shows the data description records (one or more lines of text). The content of these dialog boxes can be changed by typing in new values and pressing the Enter key or using the Cut, Copy and Paste commands of the Edit menu and the right-click pop-up menu. The groups of data records are shown in tables, with one or more columns that identify the groups by a sequence number and/or name, and show their parameters or attributes (e.g., High Limit, Low Limit, etc.). You can change the value of these parameters by clicking in each cell of the table and entering a new value and pressing the Enter key or clicking another cell to complete the change. In some cases, a pull-down list appears in the cell and you can choose a value from that list.

You can add and delete rows in the group table (and other tables) by using the Add and Delete buttons right above the table. In some tables, there is a pull-down list beside the add button from which you select one item to be added. In other tables the add button simply adds an empty row. In either case, you must type in the required data in the empty cells of the added row. You may enter a default indicator (e.g., 0 or –1) in some of the cells which can have a default value as described in Chapter 8. To delete a row, select it by clicking on it and then click the Delete button. When you select a row of the group table by clicking on the group number or a cell in that row, the composition of that group is shown in the composition table on the right of the group table. The heading of the composition table shows which row was selected in the group table. The composition in general consists of:

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Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV-list Exclude area = bus-list Exclude zone = zone-list Exclude bus = bus-list Exclude kV = kV-list The first column of the composition table shows the record identifier (e.g., Include area, Include zone, etc., without the “=” sign), and the second column shows the area/zone/bus/kV list for that record. You can change this list by clicking on it and entering a new number (or name), a list of numbers (or names) separated by “,” (e.g., “14, 15, 23”) or a range specified by two numbers separated by “:” (e.g., “101: 125”). See Section 8.1.4 for all the rules for specifying these lists. The order of the Include and Exclude records is very important and affects the composition of the group as described in Section 8.1.4. To add a new row to the composition table at a specific location, first click

on an existing row after which the new row would be added, then click the Add button (or the pull-down list beside it) right above the table. This opens the pull-down list from which you can choose one of the record types (e.g., Include area, Include zone, etc.) to be added to the table. You must then type in an area/zone/bus/kV list in the second column of the added row. If the “Name” option is selected in the Parameter data (see Section 8.4), areas, zones and buses in the Include/Exclude lists and everywhere else in all data files must be specified by their names (exactly as they appear in the powerflow data), otherwise, they must all be specified by their numbers. As in the example in the above figure, some data files contain more than one type of data groups or records. In these cases the tables of groups/records of each type are shown under a separate tab (e.g., Voltage Limits, Delta-V Limits, etc.).

3.4.2 Parameter Data View

To view and modify the parameter data click on Parameter in the data tree of the Scenario window as shown in Figure 3.15. The right side of the window shows the value of parameters in the Parameter file in dialog boxes, organized under 8 tabs (Functions, PF Controls, etc.). For those parameters which are not specified in the file, their default value will be shown. You may change the value of any parameter by typing a new value or choosing a value from the drop-down list in the dialog boxes. Refer to Section 8.4 (Parameter File) for the description of function (meaning) of each parameter and the type and range of its value. The Report range and Zone report tables show the include area/zone/bus records similar to other composition tables described in Section 3.4.1.

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3.4.3 Transfer Data View

To view and modify the transfer data, click on Transfer in the data tree in the Scenario window. The right side of the window shows the contents of Transfer file under 4 tabs, as shown in Figure 3.16

Figure 3.15: Parameter data view

Figure 3.16: Transfer data view

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Figure 3.17 View of Transfer Source

The General tab shows the transfer type as well as the Name, Description, Step Size and Cutoff Step Size in the Transfer file. If the transfer does not include Source Y, the transfer type will be one-dimensional, otherwise it will be two-dimensional. To add Source Y to a one-dimensional transfer, click the 2-

Dimensional radio button and to delete Source Y of a two-dimensional transfer, click the 1-Dimensional radio button. As show in Figure 3.17, the Source X tab shows the name of Source X and its Decrease Limit, Increase Limit and Source/Sink Groups table. This table shows the generation, load and DC converter groups and phase-shifters belonging to Source X and their related information. Similarly, the Source D (Y) tab shows the name, limits and groups of Source D (Y). Refer to Section 8.5 (Transfer File) for the description and purpose of these data items.

To add a Generation Scale, Generation Schedule, Load Scale or DC Converter group to the Source/Sink

Groups table, click on the Add button above this table and select a group from its drop-down list. You must type in a value in the Share cell and select a value from the pull-down list in the Option cell for the added group, unless these cells are grayed out. You must also specify the composition of the added group as described below.

When percent of share for two or more generation groups are set to zero, then, VSAT program

automatically assigns the percent share in each group according to the available spinning reserve of all

on-line units in each group. Note that, in order for this option to take place, percent share of all groups

should be set to zero.

As in other tables, to delete a group click on its row in the table and then click the Delete button. Click on a load or generation scale group in the table to view and edit its composition (included and excluded areas/zones/buses/kVs) in the right table as described in Section 3.4.1. Click on a generation schedule group to see the list of generators belonging to this group in the right table. You can change the data in this table by clicking in a cell and typing a new value. To add or remove a generator in this table, use the Add and Delete buttons right above the list. If you first click on

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a row to select it, and then click the Add button, the new row will be added right after the selected row. The Delete All button above the table deletes all rows. Click on a DC converter in the table to view and edit the converter specification and its participation factor in the box to the right of the Source/Sink Group table (See Figure 3.18). Each participating converter must be specified in one DC converter group (each DC converter group consists of one converter). In this way, converters of a multi-terminal DC network can participate in the transfer by any given factor. Similarly, click on a Phase Shifter in the table to view and edit its specification and participation factor in the box to the right of the Source/Sink Group table.

3.4.4 Contingency Script View

To view and modify the contingency script data click on Script under Contingency group in the data tree in the Scenario window. The right side of the window shows the contents of Contingency Script file in two tables. This data consists of contingency Groups, and each group consists of one or more Subgroups of different types, e.g., Outage Branch, Outage Generator, etc. The composition of subgroups is specified by including and excluding areas, zones, buses, kVs and/or MVAs. See Section 8.9 for details of contingency script data. The left table in the Contingency Script view shows the contingency groups by a sequential number and lists their subgroups. The right table shows the composition of each subgroup selected in the left table. See Figure 3.19.

Figure 3.18: View of DC Converter in Transfer Source

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To add or delete a contingency group, click on the Add or Delete button on the top-left corner of the Contingency Groups/Subgroups table. To delete a group first select it by clicking on one of its Subgroups. To add a Subgroup in an existing Group, first select the Group by clicking in its Subgroup

cell, then click on the Add button above the Subgroup column and select an item from the drop-down

list. To delete a Subgroup, select it by clicking on it in the Subgroup column and click the Delete button above this column. To define the composition of an added Subgroup or view and change the composition of an existing Subgroup, click on it in the Subgroup column of the left table. The right table will show the included and excluded areas, zones, etc., in the subgroup. Data can be added, changed or deleted in this table similar to other composition tables as described in Section 3.4.1 To run the script and create contingencies,

(1) If the script data has been changed, save the script file by using the Save or Save as command of the File menu.

(2) Choose Full-set or Screened in the Create Contingency File box by clicking on one of the radio

buttons depending on which file you want to be created by the script. Make sure a filename has been specified for the Full-set or Screened Contingency in the scenario (in the Contingency data view) for the script to create it. If the file exists, it will be overwritten by running the script.

(3) Click the Run button in the Create Contingency File box and view the messages that show

running of the script.

Figure 3.19: Contingency Script data view

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3.4.5 Contingency Data View

To view and modify the contingency data of a scenario, click on Full-set or Screened under Contingency group in the data tree of the Scenario window, as shown in Figure 3.20. The right side of the window shows the Full-set or Screened Contingency window. These views, which are similar except for the Screen button described below, show the list of contingencies on the left, and the contingency definition on the right.

On the right of the Contingency table there is a list of all types of outages (or changes) that can be included in each contingency. By clicking on each contingency in the left table, the symbol and number beside each outage type in the list indicate whether the selected contingency contains that type of outage. The box below this list shows the complete definition of the selected contingency (all records of line outage, generator outage, etc.) as described in Section 8.10 (without the {Contingency…}, Contingency Name and {End Contingency} records). You can change the name of each contingency by clicking in the Name column and typing in a new name. Each contingency is flagged as “Must Run”, “To be Screened” (or “Run”), or “Don't Run” as shown in the Run Flag column in Figure 3.21. To change the run flag of a contingency, click on it and from the drop-down list, select a different run flag.

Figure 3.20: Contingency data view

Figure 3.21: Contingency name and Run

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To delete a contingency, select it by clicking in its row in the Contingency list and then click on the

Delete button above the table. Click on the Add button above the table to add a contingency. You must type in a name and select a Run Flag for the added contingency in this table (as described above) and then specify its outages. To specify or modify the outages of a contingency, first select the contingency by clicking on its row in the Contingency table to view its outages in the Outage box. Then to add, delete or modify an outage type, for example a branch outage, double click on Branch in the outage list on the right of the table (see Figure 3.22). This opens the Edit Outage Branch window where the branch outages of the selected contingency are shown in a table. You can add or delete outages in this table by using its Add and Delete buttons, and change the specification of each branch outage by typing in the cells of this table. When finished changing the outages, close the Edit Outage Branch window by clicking on its Close X button on its title bar. Similarly you can add, delete or modify Bus outages, Generator outages, etc., for each contingency. See the description of outages in Section 8.10 for specifying the required data in the Edit Outage windows. The changes made in these windows will be reflected in the Outage box.

For security assessment of each scenario, (1) If you don’t want to screen the contingencies before security assessment, specify (and change and

save) the Screened Contingency file in the Screened Contingency view (or create it from the contingency script). In this case you don’t need to specify the Full-set Contingency file.

(2) Otherwise, specify the Full-set Contingency file (or create it from the contingency script) and

Contingency Screening Parameter file and run the screening to create/replace the Screened Contingency file. To run the screening, after saving all changed data files in the Scenario window (you can use the Save All command of the File menu), click on the Screen button in the upper right corner of the Full-set Contingency view (in the Client-Server version, you must have a server running; see Section 4.3 for details). After screening, you may examine, modify and save the created Screened Contingency data before security assessment.

3.4.6 Generator Capability Data View

To view and modify the generator capability data of a scenario, click on Generator Capability in the data tree of the Scenario window, as shown in Figure 3.23. The right side of the window shows the Capability Data, Capability Curves, Fixed MVAr Limits, Fixed Power Factor, and Induction Machines in the file under five separate tabs. The Capability Data, Fixed MVAr Limits, Fixed Power Factor, and Induction Machine tabs show the corresponding data in a table where you can add or delete rows and change the data in each cell similar to other tables.

Figure 3.22: Edit Outage Branch window

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The Capability Curves tab shows the capability curves in two tables. Each Capability Curve group in the data file consists of the generator bus, ID, terminal voltage, and the points of the curve. Each such group is shown in the left table as one row with the first three data items. The points of the curve are shown in the right table. Use the Add and Delete buttons above the left table to add and delete groups of capability curves data. To view and modify the points of the curve in each group, select that group in the left table by clicking on its row. The right table will show the points of the curve as a set of P, Q-hi and Q-lo values. Use the Add and Delete buttons above the right table to add or delete points on the curve or type in new values in each cell to change it. See Section 8.13 for full descript of this data. The groups of curves for each generator and the points of each curve must be specified in the correct order described in Section 8.13

3.4.7 Load Conversion Data View

Click on Load Conversion in the data tree of the Scenario window to view and modify the load conversion data of the scenario in the right side of the window. The load models specified in the data file are shown in the Exponential Load Models table. Each row shows one model by its model number and 12 coefficients and exponents for real and reactive part, as described in Section 8.16. You can modify these values by typing new values in the cells, or add and delete rows by using the Add and Delete buttons above this table. The data for the load conversion groups are shown in three tables at the lower part of the window, as shown in Figure 3.24. The Group table simply shows the list of groups by a sequential group number. Groups can be added and deleted by using the Add and Delete buttons above this table.

Figure 3.23: Generator Capability data view

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When you select a group by clicking on it in the Group table, the loads belonging to the selected group are shown in the second table and the specification of load components for this group is shown in the third table. You can add or delete rows or change the existing ones in the second table (Loads of Group n) similar to other composition tables as described in Section 3.4.1. The Load Components table allows up to 5 components to be specified for the selected group. The component in the last row, which is Constant Power, is not specified explicitly or saved in the data file. If the group’s load has, for example, only 3 components (beside the constant power component), two rows in the table remain “blank”. You can select the type of any of these 5 components from the drop-down list in the Type cell. If the selected type is Exponential Model, the model number must be entered in the Model cell (this must be one of the models defined in the Exponential Load Models table in this data or in the powerflow data). To delete one of the components, change its type to “blank”. The percentage of each component in the total real and reactive load is shown, and can be changed, in the last two columns of the Load Components table. The percentage of the constant power component in the last row is computed as 100 minus the sum of percentages of the other components. If all 5 components have been specified (i.e., none is “blank”), the percentage of constant power component must be zero since there is no room for a sixth component in the model.

3.4.8 Generator Coupling Data View

To view and modify the generator coupling data of a scenario, click on Generator Coupling in the data tree of the Scenario window. The right side of the window shows the Combined Cycle Generation Plant (CCPP) window. As shown in Figure 3.25, this view shows the list of CCPP trains on the left, and the train definitions on the right.

Figure 3.24: Load Conversion data view

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Use the Add and Delete buttons above the left table to add and delete CCPP trains (generally a “train” defines a generation plant). You can change the name of each train by clicking in the Name column and typing in a new name. The upper table on the left side lists the generators in a train. The table below this list shows possible generation output combinations of the train. It should be noticed that the order of the numbers of a row in the MW Output table must be consistent with the order of the generators in the CCPP Generators table. The numbers of a row in the MW Output table should be separated by commas.

3.4.9 Other Data Views

By clicking on other data types in the data tree of the Scenario window, the corresponding data is shown and can be modified in the right side of the window in tables and dialog boxes. These are similar to the general tables described in Section 3.4.1.

Figure 3.25: Generator coupling data view

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4. Running VSAT

Once scenarios have been loaded into VSAT, either by opening a Master Scenario File, or through the New and Add commands of Scenario menu, they will appear in the top part of VSAT main window. The Status column of the VSAT main window will show "Waiting" for all scenarios, as shown in Figure 4.1

4.1 Starting and Controlling the Servers

The Stand-alone VSAT does not require additional servers. But if you have installed the Client-Server version, before you can run VSAT you need to start the servers on the computers that you wish to use. You may start one (or more) server on the same computer that runs the client as well as any other computer on the network. For details on configuring your system for distributed processing, see Chapter 6. On the Server:

To start the server on each computer, use the Start | Programs | VSAT | VSAT Server menu. This starts the server in Server-io directory, as shown in Figure 4.2. Make sure you use the Start menu shortcut and not click on the VSAServer.exe itself to start it, so that the server starts with correct parameters and working directory. As each server starts, a window appears showing the port number of the server in the Title bar, several control boxes at the top, and a Message box.

Figure 4.2: VSAT Server window

Figure 4.1: VSAT main window before running scenarios.

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To disable each server from responding to clients, clear the check mark by clicking on it in the Enable

Server box. This is useful for having the full use of the server computer for a period of time for other applications. Click on this box again to enable the server. When the server is enabled, to prevent it from responding to clients other than the one running on the same computer, click the Local Client Only box to add a check mark. This is useful when there are other VSAT users on the network and you want to prevent them from using your server. Clear the box by clicking on it to enable the server for all clients. There are other controls for allowing or preventing different groups of clients to use the server. For more detail on this, contact Powertech. When the server is running a case, if you click the Stop Computations button, the run is interrupted (all results will be lost). The Server Messages box shows messages about the server status and client communications. When the server is idle, the box shows “Waiting for Client connection” message. You may clear the messages by right clicking in this box and selecting Clear. You may minimize the server window after it is started since you interface with VSAT through the client. When the server window is minimized, only a small icon is visible on the system tray on the task bar (see Figure 4.3). This icon will flash “OL” when the server is in use. By holding the mouse over the icon, a tip will appear, showing the status of the server. You may right click on this icon to get a menu for controlling the server.

To stop the server, click Stop& Close Server in the server icon menu, or click the Stop (x) button in the top-right corner. If the server is running a case, you will be asked to confirm interrupting the run (all results will be lost).

On the Client:

To control the servers from the client side and to verify that the client has found the servers, pull down the View menu of the VSAT main window and select Servers (Figure 4.4). This opens the Server List window (Figure 4.5). To find the running servers on the network and update their status, click the Find New Servers button. After a short delay for response from the servers, all running servers will appear in the list with Status

Free (if they are not used by another client) or Busy (otherwise).

Figure 4.3: Server icon menu

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To enabled or disabled a server for this client only, click on it in the Enabled column to add or remove the check mark, as shown in Figure 4.6 (or click on ID to select the server, and then click on the Enable/Disable button). Disabled servers will not be used by this client.

If a running server doesn’t appear in the list, you can add it manually by clicking the Add button. The New Server window will pop-up. Enter the server name or IP address and port number then click OK. Generally the list shows all running servers and you don’t need to manually add servers or click the Find

New Servers button to update the list.

4.2 Converting Powerflow Data

Before any computation, if the powerflow data of a scenario is contained in a file other than a binary PFB (or PSF) file, you must convert it to PFB by the following procedure: (1) Double click on the desired scenario row in the top part of the VSAT main window to open the

Scenario window.

Figure 4.5: Server List window

Broadcast to find servers

Enable/Disable a server

Manually add a server

Figure 4.4: View Servers menu

Figure 4.6: Adding a server

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(2) Double click on Powerflow on the left side, to see the Powerflow dialog on the right side of Scenario window.

(3) If needed, specify or change the Powerflow Format, Powerflow Filename and PFB or PSF

Filename in this dialog by clicking on the pull-down or browse button beside each box. (4) Click the Convert to PFB button and check the messages that appear to make sure the data is

correctly converted and saved in the PFB file. If needed, you can also request a powerflow solution

after converting the file, see Figure 4.7

(5) Exit Scenario window.

See Section 3.3 for more details.

4.3 Screening Contingencies

If you have specified the (Screened) Contingency data for all scenarios (whose Contingency Analysis parameter is True in the Parameter data), you can run the Security Assessment without further screening of contingencies. But if for a scenario this data is not specified or needs to be updated (if the Powerflow, Transfer or Margin data have changed since the previous screening), you must run the Contingency Screening for that scenario to create/update the Screened Contingency data from the Full-Set Contingency data. This is done in two ways as follows. From the Main Window:

You can go to the Screening window directly from the VSAT main window if the scenarios are setup and there is no need to modify the data. For this, pull down the Analysis menu and select Contingency

Screening as shown in Figure 4.8. This opens the Contingency Screening window (Figure 4.9) where there is a tab for each scenario. To perform the screening for a scenario of interest, click on its tab.

Figure 4.7: Converting Powerflow data

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The left side of the window shows the list of contingencies specified in the Full-Set Contingency File. The right side of the window shows the list of contingencies in the Contingency File if this file exists. Otherwise, the right side will be empty. To start the screening for the selected scenario, click on the Run button on the upper right corner of the window. The Message window will appear, showing the messages and progress of the computation. Check these messages to make sure the Screened Contingency data is created correctly, and then close the Message window by clicking on its Close (x) button on the upper right corner. When the screening completes successfully, the screened contingency list is stored in the Screened Contingency file and a message indicating the completion of screening appears on the status bar at the bottom of this window. You need to repeat this process for every scenario that needs screening (click on its tab, then click the Run button). When finished, close the Screening window by clicking on its Close (x) button on the upper right corner to return to the VSAT main window.

Figure 4.8: Opening Contingency Screening window

Figure 4.9: Contingency Screening window

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From the Scenario Window:

Alternatively, you can screen the contingencies from the Scenario window (see Figure 4.10), especially when you need to modify the data and repeat the screening. For this: (1) Double click on the desired scenario row in the top part of the VSAT main window to open the

Scenario window. (2) Double click on Full-Set Contingency on the left side, to see the Full-Set Contingency dialog on

the right side of Scenario window. (3) If needed, replace the Full-Set Contingency file, and/or change Run flag and description of

individual contingencies in this dialog. See Section 3.4.5 for more details. (4) Similarly, if needed, modify the Contingency Screening Parameter data. (5) Save all changed data, including the Scenario file, using the File menu of the Scenario window. (6) Click on the Screen button in the upper right corner of the Full-Set Contingency dialog. This

opens the Screening window, where you can run the screening as described above. (7) Check the messages that appear to make sure the Screened Contingency data is created correctly.

Then close the Screening window by clicking on its Close (x) button on the upper right corner (8) You will return to the Screened Contingency dialog, where you can examine and, if needed,

modify and save the screened contingencies for the security assessment run. (9) If the list of screened contingencies is not satisfactory, modify the parameters or the Full-Set

contingencies and repeat the screening. Otherwise, (10) Return to the VSAT main window by using File | Exit menu of the Scenario window or its Close

(x) button.

Figure 4.10: Contingency screening in Scenario window

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4.4 Enabling/Disabling Scenarios

Since a large number of scenarios can be loaded in VSAT either manually or through a Master Scenario

File, the user may wish to run only selected Scenarios without creating a new Master Scenario File.

When loaded, all scenarios are set to run as indicated by a check (√) mark in the Run column. Clicking on the check box toggles the Run flag (between set and clear) to run or not to run the scenario. The Analysis menu allows you to set or clear all Run flags or invert (toggle) them. See Figure 4.11.

4.5 Running the Security Assessment

To run the Security Assessment, pull down the Analysis menu in the VSAT main window and select Run

Security Assessment (as shown in Figure 4.12), or alternatively, hit the Run button � on the tool bar. This will run the security assessment for all the enabled scenarios by distributing them to available servers. (If you haven’t specified the Contingency file or wish VSAT to update this file, you need to run the Contingency Screening as described in Section 4.3 before running the Security Assessment). When the run is completed, the VSAT main window will show:

• "Finished" in the Status column

• Transfer limit in the Limit column (for one-dimensional transfer only; two-dimensional transfers do not have a single limit)

• Bar charts of secure ranges and table of security limits and violations of one-dimensional transfers under the Range Scenarios tab

• XY plot of secure region and table of security limits and violations of each two-dimensional transfer under separate tabs

• Run messages of each scenario under separate tabs in the Message window (lower part of the main window)

Figure 4.11: Enabling/disabling scenarios for run

Figure 4.12: Running Security Assessment

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4.6 Viewing the Limits and Violations

VSAT main window provides a graphical and tabular display of the computation results (Figure 4.13).

When the run starts, the Base Level column in the Scenario table shows the value of source or sink (Source X or Source D) for one-dimensional transfer, or Source X and Source Y for two-dimensional transfer, in the base case. When the run is completed, the Limit column shows the value of source or sink at the transfer limit. For one-dimensional transfer, click on the Source(s) column in the table allows you to select between source and sink. For scenarios with one-dimensional transfer or no transfer, under the Range Scenarios tab, a bar chart shows the progress of the computation in the form of an advancing green and yellow bar. When the computation is completed, the green part of the bar indicates the secure range of the transfer. The insecure (or un-computed) range of the transfer becomes red. The yellow part indicates either one step of transfer (distance between the last secure and first insecure transfer level) or, if “Transfer Analysis” is “To Maximum” (see section 8.5), all the steps where insecurities are found. When the base case is insecure and transfer is reversed (see section 8.5), the reversed range of transfer is shown in orange and the point where the case becomes secure is shown in green. The bar represents either the source or sink of the transfer as selected in the Source(s) column of the Scenario table (which can be toggled by right click in the Source column). The blue arrow indicates the base value and direction of change in the source or sink.

Figure 4.13: Security limits of one-dimensional transfers

Transfer Limit

Transfer in the Base Case

Transfer in the Base Case

Transfer Limit

Insecure Transfer Levels

Contingency that causes insecurity

Type of insecurity

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The table beside the bar charts shows the detail of insecurities related to the yellow (or orange) part of the bar charts. It shows the value of source and sink where insecurity is found, the contingency that causes insecurity and the type of insecurity (violated criteria). For scenarios with “Transfer Analysis = To Maximum”, computation continues beyond the first insecurities (where the bar changes to yellow) until the pre-contingency case becomes voltage unstable, or the maximum transfer is reached (where the bar changes to red). See Figure 4.14. All insecure points and violations are listed in the table beside the bar charts. Initially, one row shows the first insecurity for the scenario (as in the above figure), but by clicking on the + sign beside the row, it expands to show all insecurities. In this case, the + sign changes to - sign which can be clicked to collapse the list back to one row.

For scenarios with one-dimensional transfer, if the base case is insecure, the Limit column of the Scenario table shows “Insecure”, but if the transfer is reversed and a secure point is found, the value of Source X (or D) at the secure point is shown in the Limit column inside brackets. For scenarios without a transfer (“Transfer Analysis = No” in the Parameter data), the transfer columns remain blank. If there are no violations (the case is secure), the Limit column of the Scenario table and the Violation column of the table beside the bar charts show “Secure” and the whole bar is shown in green. Otherwise, the Limit column of the Scenario table shows “Insecure”, the whole bar is shown in red and the insecurities are shown in the table beside the bar charts. For scenarios with two-dimensional transfer (see Figure 4.15), under separate tabs with the Scenario-id label, the progress of the computation is shown in the form of advancing radial lines in an XY plot region. The region of secure points (green dots) is the secure region of the transfer and is colored green. The colored dots outside the secure region are the computed insecure points are shown in the table beside the plot. The color of the dot indicates which security criterion is violated at that point. By clicking on a colored dot on the plot, the coordinates of that point are displayed and the corresponding row of the limit table is highlighted. When there are several violations at one point, the table shows several rows for that point and the priority for coloring the dot is in the following order:

• Instability (red)

• Margin violation (orange)

• VAr Reserve violation (yellow)

• Voltage violation (blue)

• Overload (purple)

Figure 4.14: Security limits with “Transfer Analysis = To Maximum”

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If you click on Instability button below the plot, the unstable points are highlighted and their region is colored red. Another click on this button cancels the highlight. Similarly, you can highlight the points/region of Margin violation, VAr Reserve violation, etc. When “Transfer Analysis” parameter is “To Maximum”, all violations are highlighted. The priority for coloring the regions when they have several different violations is the same as that for coloring the dots (listed above). The region between the secure points and insecure points is colored light green. You can still highlight one violation at a time (for example, highlight Overload region if it is covered by Margin violation) by clicking on its button below the plot. Another click on the button cancels the highlight. The color assigned to each type of violation can be changed by double clicking on its button below the plot and selecting a color from the pallet. The base point is indicated by a blue star in the plot. If the base point itself is insecure, VSAT finds a secure point (by reducing X, Y and/or D) and computes the secure region in radial directions from this secure point, unless the minimum X, Y or D is reached before finding a secure point.

4.7 Viewing the Messages

During the computations, messages and results of each scenario are stored in the Progress Report and other output files (see Chapter 7). Key messages are also displayed in the Message window and can be viewed during computations, as shown in Figure 4.16. The Messages window is initially positioned in the lower part of the VSAT main window. You may tear off this window by holding its handle (the bars on the right border) and dragging it to another location.

Figure 4.16: Message window (when torn-off the VSAT main window)

Figure 4.15: Security limits of two-dimensional transfers

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If you close the Message window (by clicking its x button after you tear it off from the main window) you can reopen it from the View | Messages menu of the VSAT main window. For each scenario there is one tab on the lower border of the Message window. There is also one tab marked General that is used for common messages such as reporting total time spent on all of the scenarios, etc. To access the messages of a scenario, click on the corresponding tab. To clear the messages after a run, click the right mouse button in the Message window and select Clear

from the menu that will pop-up. You may also select Copy or Save from this menu to copy the

messages to the clip board or save them in a text file.

4.8 Viewing and Plotting the Results

Details of security violations and transfer limit, along with monitored variables and other user-requested reports of computed scenarios are saved in the output files. To view/plot the results, open the DSA Output Analysis module by the Output Analysis command of the Results menu in the VSAT main window. See the DSAOA Manual for details.

4.9 Running VSAT Batch

VSAT has a “batch” version (vsat_batch.exe) that can be used to run one scenario at a time. It does not have a graphical user interface and distributed processing capability. It can be used in a batch process to run scenarios without user interaction. Scenario files must have been prepared manually (see section 3.1) or in VSAT GUI (see section 3.2) before running them in VSAT batch. To run VSAT batch, open a DOS prompt window and go to the directory where you want to run VSAT and type, xxx\VSAT\bin\vsat_batch.exe

Where xxx is the path of VSAT folder (e.g., C:\DSATools_8). The program starts and prompts you to

choose an option from 1 to 4 (other values cause the program to stop): 1: Security Assessment / Transfer Limit Computation 2: Contingency Screening 3: Remedial Action 4: Operating Point for RA Choose option 1 to run Security Assessment for a scenario with or without a transfer Analysis (see section 2.2). Choose option 2 to screen the full-set contingencies for a scenario with transfer (see section 2.3) and then choose option 1 to compute the transfer limit with the screened contingencies. Choose option 3 to run Remedial Action for a scenario (see section 2.5). The program then prompts you to type in the scenario-id (identifier for the scenario, used to name the output files) and the scenario filename. After running the scenario, it prompts you again to choose an option. Option 3 runs the Remedial Action at the base point (the powerflow case specified in the scenario). To perform Remedial Action at a higher transfer level (e.g. 100 MW higher than the limit determined by option 1), first choose option 4 to create the case (Operating Point) at a specified value of transfer Source X. The program prompts you to specify the value of Source X, Xval, and saves the powerflow case after

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increasing the transfer to this value. This case is saved in file scenario-id.psn. It is recommended to rename this file to, for example, scenario-id-Xval.pfb (change the type from .psn to .pfb; Xval could be

the value you specified for Source X). You must then create a scenario file with “PFB File =

scenario-id-Xval.pfb” (you might prepare this scenario by modifying the original scenario and

replacing its PFB file; this can be done once if you use a fixed name for the new PFB file). Then choose option 3 and provide this new scenario to perform Remedial Action at the specified transfer level. The above information can be provided as arguments to the program by typing, xxx\VSAT\bin\vsat_batch.exe Option ID Scenario-filename [Xval]

Where Option must be from 1 to 4 as described above and ID , Scenario-filename and [Xval]

(needed only for option 4) are the same as those in interactive run.

In this case, the program stops after running one option, so you must repeat the above command with different arguments to run different options and/or different scenarios. This form is useful for being included in a batch script that would run without user interaction. Another way of running VSAT batch without user interaction is to run it (directly or in a batch script) without arguments, but direct the input from a file rather than the user keyboard. For example if you prepare a file, vsat_batch.dat, containing: 2

id1 t1.snr 1 id1 t1.snr 1 id2 t2.snr 0 Then,

xxx\VSAT\bin\vsat_batch.exe < vsat_batch.dat Will run Contingency Screening and Security Assessment for scenario t1 and Security Assessment for scenario t2 and stops.

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5. Remedial Action

The Remedial Action (RA) module of VSAT finds the best available control action to make an insecure operating point secure. This chapter describes the data requirements and operation of RA.

5.1 RA Data Requirement

Two data files are needed for computing the remedial actions: (1) Remedial Control Data: describes the available controls, their priorities, etc. (2) Sensitivity Parameter Data: provides the parameters for the sensitivity-based remedial action

computation To select, view and modify these data files for a scenario: (1) Double click on that scenario in the VSAT main window to go to the Scenario window, and in the

left section of that window click on Control or Sensitivity Parameter under Remedial Action group (as described in Section 3.2.3). See Figure 5.1.

(2) You may examine, modify and save these data files by using the Edit and File menus. The format and meaning of data in these files are described in Sections 8.23 and 0

(3) If you changed a data filename, save the Scenario file by using the File | Save (As) Scenario menu

and Exit the Scenario window.

Figure 5.1: Remedial Control view in Scenario window

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5.2 Running RA

To run the RA module, in the VSAT main window pull-down the Analysis menu and select Remedial

Action, or click on the RA button on the tool bar. The Remedial Action window will appear (Figure

5.2). To run RA, in the Remedial Action window do the following: (1) In the Select Scenario pull-down list, select the desired scenario. (2) If, for example, the operating point at 4200 MW transfer level is insecure in the selected scenario,

and you wish to find the remedial action for making this point secure, type 4200 in the Select the

Operating Point …edit box. To select the base (initial) operating point, if the scenario does not involve a Transfer (“Transfer Analysis = No” in the Parameter data) you must type zero (0) in this edit box, otherwise, you must type in the value of transfer's source X at the base point (as shown in the VSAT main window).

(3) Pull down the Run menu and select Remedial Action (Figure 5.3). (4) VSAT first creates the specified operating point and then runs the RA module. The bottom of RA

window shows the processing steps and the messages from computation engines are displayed in the VSAT Message window under the tab for the selected scenario.

(5) When RA computation is finished, the Results box of the RA window shows the Preventive and

Corrective controls for making the selected operating point secure (Figure 5.4). These results are also saved in the RA results file (scenario-id-ras.rpt).

(6) You may type a different value in the Select the Operation Point … box and run RA again. (7) To exit from the RA window, click on the x button or select the File | Close menu item.

Figure 5.2: Remedial Action window

Figure 5.3: Running RA

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Figure 5.4: Remedial Action results

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6. Distributed Processing Setup

VSAT can be configured for distributed processing using a single client (must be a PC running Windows XP, Vista, or Windows7) and any number of servers (see Sections 2.6 and 2.9). The client and server computers may be connected either only to each other (a stand-alone network), or to an existing network.

6.1 Stand-alone Network Connection

Each PC that is used to run the VSAT Client and/or Server must be equipped with some TCP/IP compatible network interface card and be connected to one another over a valid TCP/IP network (Token Ring, Ethernet, etc). For example, two PCs equipped with Ethernet cards each connected to a central hub would be a valid configuration. The only modification required for using a stand-alone network is that the windows HOSTS file C:\windows\hosts on Windows 95/98 C:\WinNT\system32\drivers\etc\hosts on Windows 2000/NT/XP Must be modified to include the mapping of the IP addressees to the Host names for all the machines on the network as shown in Figure 6.1.

Figure 6.1: Adding IP address and hostname to HOSTS file

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6.2 Existing Network Connection

VSAT is designed to run on most of the existing TCP/IP capable networks without additional requirements. Simply, install the VSAT Client and/or Server on any PC on the network that you intend to use for running VSAT. Note that servers make full use of all available CPU resources, which may cause any other application running on the server machine to slow down.

6.3 Configuring Networked Computers

If you experience problems with VSAT client-server communication on the network, go through the following checklist (make note of any changes you make so that you can undo them if needed): For Windows 95/98

(1) Open the Network icon from the Windows Control Panel and select the Identification tab and write down the Computer Name.

• Control Panel � Network icon � Identification tab � Make note of the Computer Name. (2) Select the Configuration tab, then select network adapter for your networking card from the

Installed Component list and click the Properties button. Under the Bindings tab, ensure the adapter’s bindings are set to use the TCP/IP protocol.

• Configuration tab � Select Network Adapter � Click Properties � Bindings tab � Is TCP/IP present?

(3) If any changes have been made go back to the Networks Settings window by clicking OK. Select

the TCP/IP protocol from the Installed Components list and click the Properties button. (If this is not in the list the TCP/IP protocol has not been installed for windows, it can be added by clicking the Add button, selecting Protocol, clicking the Add button, selecting Microsoft and TCP/IP and clicking OK.)

• Click OK � Networks Settings window � Select TCP/IP protocol � Click Properties (4) Click on the DNS tab, If the Enable DNS is checked make sure the Host Name matches the

Computer Name from step 1 (these names are case sensitive), also ensure the Domain is correct for your network, e.g. Powertech.bc.ca (Note: DNS would most likely be disabled for stand-alone networks)

• DNS tab � Is DNS enabled? � If so, are the Host Name and Domain Name correct? (5) Click on the WINS Configuration tab, if WINS Resolution is enabled and you are experiencing

problems running VSAT you may want to try Disabling WINS Resolution, otherwise leave it as is. You may also try the Bindings tab and see if checking Client for Microsoft Networks makes a difference.

• Bindings Tab � Is Client for Microsoft Networks checked? If you have made any changes go back to the Network Settings window by clicking OK, and clicking OK again. Windows should now be restarted with the new network settings. For Windows NT

(Administrator access will be needed to view some of the following information on NT)

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(1) Open the Network icon from the Windows Control Panel and select the Identification tab and write down the Computer Name.

• Control Panel � Network icon � Identification tab � Make note of the Computer Name

(2) Click on the Protocols tab and select the TCP/IP Protocol from the Network Protocols list and click the Properties button.

• Protocols tab � select TCP/IP Protocol � Click Properties (3) Click the IP Address tab and ensure your network adapter is listed under the Adapter List.

• IP Address tab � Adapter List � Is your Network Adapter listed? (4) Click on the DNS tab, make sure the Host Name matches the Computer Name from step 1 (these

names are case sensitive), also ensure the Domain is correct for your network, e.g. Powertech.bc.ca

• DNS tab � Are the Host Name and Domain Name correct? If you have made any changes go back to the Network Settings window by clicking OK, and clicking OK again. Windows should now be restarted with the new network settings.

6.4 Configuring Stand-alone Computer

On a stand-alone computer (not connected to a network), it is better to install and run the stand-alone VSAT, since the computer cannot take advantage of multiple servers. If you install the client-server version of VSAT and your computer is not on the network (e.g. you use your laptop outside your office), VSAT client may not be able to find the server running on the same computer. To fix the problem: For Windows 95/98

(1) Open the Network icon from the Windows Control Panel and select the Configuration tab, then select network adapter for your networking card from the Installed Component list (e.g. TCP/IP in the list) and click the Properties button. Under the DNS Configuration tab see if Enable DNS is selected and note the Host (e.g. pli1234) and Domain (e.g. Powertech.bc.ca) names. Note that these names are case sensitive.

(2) Open the C:\Windows\hosts file in an editor (e.g. Notepad) and at the end of it add localhost and

Host/Domain names as:

127.0.0.1 localhost 127.0.0.1 HostName

where HostName is the name found in step 1 (e.g. pli1234) or HoastName.DomainName (e.g. pli1234.Powertech.bc.ca) if Host name alone does not work.

For Windows NT

(1) Open the Network icon from the Windows Control Panel and select the Identification tab and write down the Computer Name (e.g. pli1234).

(2) Open the C:\WinNT\system32\drivers\etc\hosts file in an editor (e.g. Notepad) and at the end of it add localhost and Computer name as:

127.0.0.1 localhost 127.0.0.1 ComputerName

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where ComputerName is the name found in step 1 (e.g. pli1234) For Windows 2000

(1) Open the Network and Dial-up Connections icon from the Windows Control Panel, pull-down the Advanced menu and select Network Identification. Write down the Full Computer Name. (e.g. pli1234)

(2) Open the C:\WinNT\system32\drivers\etc\hosts file in an editor (e.g. Notepad) and at the end of it add localhost and computer name as:

127.0.0.1 localhost 127.0.0.1 FullComputerName

where FullComputerName is the name found in step 1 (e.g. pli1234)

(3) If the client can not find the server, you need to disable Media Sensing as follows:

• Go to Start menu on the task bar and select Run, type Regedt32 in the Open box and click OK.

• In the Registry Editor window that opens up, select HKEY_LOCAL_MACHINE window and go to System\CurrentControlSet\Services\Tcpip\Parameters on the tree on the left side of the window. The right side shows the values (if not, pull-down the View menu and select Tree and Data).

• Pull-down the Edit menu and select Add Value. In the Add Value dialog, type: Value Name: DisableDHCPMediaSense Data Type: REG_DWORD –Boolean and click the OK button, or, if the value already exists, double click on it to change its data.

• In the DWORD Editor dialog, type Data: 1 and click the OK button.

Later, when you connect your PC to a network, you should cancel this (so that the IP address of your PC gets updated automatically) by double clicking on this Value and in the DWORD Editor, changing Data to 0.

6.5 Setting up Multiple Servers on a Single PC

Multiple servers can be run on a single PC simply by running the VSAT server multiple times. This can be useful for taking advantage of multi-core CPU’s as each server will only take advantage of a single CPU core.

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7. Output Files

VSAT creates a number of output files for each scenario completed. It uses the scenario-id (plus additional identifier if required) and designated file extension to name the following output files: scenario-id.prg is the progress report (main output) file of the security assessment, which

contains the descriptions of input data and powerflow solution of pre- and post-contingency cases at different points of the Transfer.

scenario-id.lmt shows the voltage security limit summaries. For one-dimensional transfers, it

shows the transfer limit, the violation that limits the transfer, and the contingency that causes the violation. For two-dimensional transfers, similar information is provided for each computed boundary point of the secure region.

scenario-id.pvt contains the tables of all monitored variables specified in the Monitor file. scenario-id.pvp contains the monitored variables arranged in a format that is ready for plotting.

This file can be read by DSAOA to produce PV and similar plots for any of the monitored variables.

scenario-id-xxx.rpt where xxx may be (i) bus, gen, itf, ckt, flw, dcs, smz, lsz, which contain the

various reports specified in the Parameter file for Bus, Generator, Interface Flow, Circuit Flow, Branch Flow, HVDC Solution, Zone Summary, and Zone Loss reports; (ii) vlt, qrs, ovl, mod, sps, which contains voltage limit violations (if any) in scenario-id-vlt.rpt; MVAr reserve violations (if any) in scenario-id-qrs.rpt; thermal limit violations (if any) in scenario-id-ovl.rpt; modal analysis results (if any) in scenario-id-mod.rpt; and applied SPS (RAS) actions in scenario-id-sps.rpt. Most of the security violation reports can be shown in DSAOA in various graphical formats for easy examination.

scenario-id.vqp contains the results for the VQ curves specified in the VQ Curve file. This file

can be read by DSAOA to produce VQ curve plots. scenario-id.dsa contains the descriptions of source/sink changes at each transfer increase step, as

well as the descriptions of outages/changes of each contingency. scenario-id.cao contains the results of the contingency screening, including the descriptions of

the input data and screening process. At the end, the screened list of contingencies is shown.

scenario-id.ras contains the progress report of the RA analysis. scenario-id-ras.dtl shows the control selection process and result of each stages of the RA analysis. scenario-id-ras.rpt shows the final results (identified remedial actions) of the RA analysis. All of these result files can be viewed in DSAOA, which is accessed by the Results | Output Analysis menu command. The major results are displayed in DSAOA in various graphical formats. In addition to the above result files, powerflow cases in PFB format can be saved at any point during a transfer analysis as specified in the Parameter file.

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8. Input Data File Formats

8.1 General Rules

The following general rules apply to VSAT input data files (with the exception of the powerflow data). Exceptions to these rules are described in the sections for individual data files.

8.1.1 Data File Structure

In general (except when otherwise indicated), a VSAT data file starts with an identifier record in the form of: [VSAT n.m XXX]

where n.m is the VSAT version number (e.g., 9.0) and XXX is the name of the data such as Parameter,

Transfer, etc. VSAT accepts data files of previous versions (e.g., VSAT 9.0 accepts [VSAT 5.0 Parameter] data file). For most data files, the newer versions have the same format as the old versions but may have new data records or accept new values for data items. However for some data files the format of some of the records in the old and new versions might be different. For these files you must make sure to specify the correct version number in the above identifier record.

The end of data is identified by the End record: [End]

Any data after the End record is ignored. Data records in the file have the general form of: Data identifier = value(s) and/or keyword(s)

where Data identifier is a fixed descriptor as in: Outage Branch = 1201 1202 'A' In some data files, a group of related records must be specified together. In this case the group is

specified by Header and End records in the form of: {YYY} group's record 1 group's record 2

. . . {End YYY}

where YYY is the group identifier such as Load Scale Group. The file, group, and data identifiers are case-insensitive and can be preceded or followed by any number of blanks. However, the spelling of the identifiers (including spaces between words) is fixed. Any record starting with / is considered a comment and ignored, as are the blank records: / Comment

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Important: the Tab key must NOT be used in any data file as white space. Space key must be used for such purpose.

8.1.2 Data Records

In general (except when otherwise indicated), data values (following the identifier and the equal sign =) are format-free. Therefore, character strings such as names and IDs must be enclosed in single quotes.

Some records have keywords such as Yes or Always. These keywords are not enclosed in single quotes. Commas (and extra blank spaces) between the data values are optional. Comments can be added on each record after the last data item and a slash /, as in the following example: Identifier = 'abcd' 1.2 3.45 / in-line comment In many places defaults are assigned to variables if data is not provided for them (or if a specific value, such as 0, is provided). These defaults are described for each input data in the following sections. For example, suppose a record must have three integer values for variables A, B and C, and the program provides default values for variables B and C. Then the record Identifier = 100 200 / or Identifier = 100, 200, , results in variable C being assigned with its default value. Also, record Identifier = 100, , 300 or Identifier = 100 0 300 results in variable B being assigned with its default value (assuming that 0 is the specific value indicating default for B). Note that the commas and/or terminating slash / must be included on a record with missing data,

otherwise the record is not accepted (e.g., Identifier = 100 200 is invalid in the above example). Also, if the program does not have default value for a variable, you must give a value for it, otherwise, it

may take an unknown value (e.g., if 100 is replaced by a comma in the above examples, the value of A becomes unknown.)

8.1.3 Name Option

In VSAT, a power system component can be identified by its bus number(s) (and ID), bus name(s) (and ID), or equipment name. The details can be found in Section 8.4. The default identification method of VSAT uses bus number (and zone number, area number). To use other identification methods, for example, bus name (and zone name, area name) method, the following record must be included in the Parameter file (described in Section 8.4):

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Name Option = Name One scenario in a VSAT case can only use one identification method in every data file. When the bus name option is selected, in every data file buses, zones and areas must be specified with their names (enclosed in single quotes), i.e., you cannot use both names and numbers in one scenario. Bus, zone and area names in PFB are 16 characters long but the trailing blanks can be omitted in the data. When a list of names is specified in one record, they must be separated by comma. The names, therefore, must not contain comma or quote characters.

8.1.4 Include and Exclude Records

In several data files, a group of areas, zones or buses needs to be specified. In general, these are specified by records such as: Include area = area-list Include zone = zone-list Include bus = bus-list Include load = bus ‘id’ Include generator = bus ‘id’ Include kV = kV-list Exclude area = bus-list / or zone, bus, load, generator, kV Note that some data files accept only a subset of these records. When the Name option is selected, area_list, zone_list and bus_list are lists of names (one or more) separated by commas, such as: Include area = 'BC Hydro' Include bus = 'ABCDEFG 230.' , 'QWERT 118.' With the Number option, the lists contain one or more numbers separated by commas such as: Include zone = 511 Exclude bus = 1201, 1202, 2300 Alternatively, a range of numbers can be specified with a colon : in the form of: Include bus = 3001 : 3999 Note that the range and list cannot be mixed on one record (e.g., “3, 5:8” is not acceptable), range cannot be used with the Name option, and numbers or names in the list must be separated by commas (e.g. in “3 5, 7”, 5 will be ignored). Some data files accept records that include/exclude a specific load or generator. In this case, the record can only contain ONE load or generator. For example: Include generator = 511 '1' or Exclude load = 'GFEDCAB 115.' '2' In the following record, generator 512 ‘1’ will be ignored:

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Include generator = 511 '1', 512 '1' Examples of kV list and range (similar to bus number list and range) are: Include kV = 118.0, 230.0, 345.0 Exclude kV = 0 : 60.0

The Include and Exclude records are processed in the order that they are specified. For example, if zone 50 is in area 3, then the following records will include buses of area 3, except those in zone 50. Include area = 3 Exclude zone = 50 But, the following records include all buses of area 3 (including zone 50). Exclude zone = 50 Include area = 3

8.2 Powerflow File – PFB (or PSF) Format

VSAT computations need a base powerflow case in PFB (or PSF) binary format. The format of this data is explained in PSAT User Manual. If the base powerflow data is provided in another format (such as PTI PSS/E RAWD, GE PSLF, or other formats), it must be converted to PFB before any computation.

8.3 Powerflow File – Third Party Format

If the base powerflow case is in a third party format, such as PTI PSS/E RAWD, GE PSLF, or other, it must be converted to PFB binary format before VSAT computations. Refer to Section 3.3 on how to perform this conversion.

8.4 Parameter File

This file contains the parameters which specify the type of computations to be performed in VSAT, solution parameters, control actions, output options, etc. The first record in this file must be: [VSAT 9.x Parameter] Each parameter is then specified on one record in the form of: Parameter identifier = value

where value is an integer, real, logical (True or False) or string (keyword). Integer and real values

(typed in italic in the following) are specified in free format. Keywords are fixed strings of characters that must be entered exactly as specified below. Only one of the values that are separated by | in the following list must be specified for each parameter. As described in the general rules, identifiers and keywords are case-insensitive; keywords are not enclosed in quotes; leading and trailing blank spaces are insignificant; and tabs should not be used.

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The end of data is indicated by the optional record: [End] The parameters can be specified in any order and only those parameters whose values are different from the default values need to be included in the Parameter file. The following is the list of all parameters.

Functions Parameters Identifier Default Transfer analysis = To first limit | To all limits | To maximum | No No

When To first limit is specified, transfer (specified in the Transfer file) is computed up to its first limit (computation stops when the first security violation is found). When To all limits is specified, transfer increase (or decrease) continues until all types of violations (instability or VS margin violation, voltage violation, thermal overload, etc., depending on the specified security criteria for the scenario) are found or the maximum/minimum transfer is reached. When To maximum is specified, transfer is computed up to its maximum (or minimum), for 1-D transfers and for each direction of 2-D transfers. When No is specified, transfer is not computed (Transfer data is ignored). Contingency analysis = To first insecure | All | No No When To first insecure is specified, contingencies are analyzed one by one until one contingency causes insecurity. The rest of contingencies will not be analyzed. This is changed to All if “Transfer analysis = To maximum” or “Transfer analysis = To all limits” is selected. When All is specified, all contingencies are analyzed, even when one contingency causes insecurity. For Contingency Screening, All and To first insecure have the same effect. When No is specified, contingencies are not analyzed (Contingency data is ignored). Generation dispatch for contingencies = Governor response | AGC action | None None This specifies the powerflow dispatch option for solving contingencies. In post-contingency, the active power is balanced by Governor Response, AGC Action or, when None is specified, by the swing buses. Modal Analysis = At Stability Limit | At Point Pnt, Contingency Ctg, Before Stress | At Point Pnt, Contingency Ctg, After Stress | At Source Xmw, Contingency Ctg, Before stress | At Source Xmw, Contingency Ctg, After stress | No No

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When At Stability Limit is specified, and a voltage-unstable case is encountered, modal analysis is performed at the last stable case. For example, if contingency X causes instability at transfer step 12 after the Stress, VSAT returns to transfer step 11, applies the Stress and contingency X, and performs Modal Analysis on this case. After performing the Modal Analysis, VSAT may continue the analysis depends on the transfer and contingency analysis options selected in the parameter file. This option can also be selected in the two dimensional transfer analysis. Modal Analysis may be performed at more than one point when this option is selected. When At Point is specified, Modal Analysis is performed at Point number Pnt of transfer increase/decrease. Point 1 is the base point, Point 2 is the second point (after one step increase), etc., as seen in the VSAT messages and progress report (if Pnt is zero or negative, this record is ignored). When At Source is specified, Modal Analysis is performed when “Source X” of the transfer reaches Xmw. This option is not accepted for 2-dimensional transfers. For 1-dimensional transfers Xmw must be within 1 MW of the source value at a transfer point. For example, if Source X changes from 500 to 600 to 700, etc., Xmw=500 indicates the first point, Xmw=600 indicates the second point, etc. Xmw=605 will be ignored since it is not within 1 MW of a transfer point. If “Transfer analysis = No”, the value of Xmw is unimportant and Modal Analysis is performed at the base point. When At Point or At Source is specified, Modal Analysis is performed for contingency Ctg. Ctg is the contingency name (enclosed in single quotes) or contingency number (sequential number of “Run” and “Must Run” contingencies). When Ctg is specified as ‘Pre-contg’ or 0, Modal Analysis is performed in pre-contingency (at specified Point or Source value). When Before Stress is specified, Modal Analysis is performed at the specified transfer point and contingency before applying the stress (Margin). When After Stress is specified, Modal Analysis is performed after applying the stress at the specified point. When At Point or At Source is specified, the computation of the current scenario is terminated after Modal Analysis is performed. When No is specified, Modal Analysis is not performed.

At Stability Limit, At Point and At Source must be typed with one space between the words. There can be any number of spaces (with or without one comma) between the other words on the right side of the = sign. When At Point, At Point, or At Source is specified, a Modal Analysis Parameter file is required to provide modal analysis parameters. VQ Curve Interval = Int 0

When Int is set to a positive integer, VQ curves are computed at Int intervals of transfer

increase points (e.g., when Int is set to 3, VQ curves are computed at point 3, 6, …). To

compute VQ curves at the base point (even when “Transfer analysis” is set to “No”), set Int to 1. Note that if the Margin File is defined, VQ calculation cannot be performed. To disable

VQ calculation, set Int to 0.

When Int is set to a positive integer, a VQ Curve file is required to provide VQ analysis parameters.

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Check branch flows = True | False False When True is specified, flow of lines and transformers are checked for overload as part of the security criteria. No thermal loading check is performed when False is specified. Convert load models = True | False | Always from PF file | Always From CLD file False

The possible values for this parameter are: True: loads for post-contingency analysis are converted to the models specified in the Load Conversion file. Constant power model is used for all loads for the pre-contingency analysis.

False: constant power model is used for all loads for both pre- and post-contingency analysis.

Always From PF file: load models in ZIP format defined in the PFB powerflow data are used for all loads for both pre- and post-contingency analysis. Always From CLD file: loads are converted to models specified in the Load Conversion file for both pre- and post-contingency analysis.

When True or Always From CLD file is specified, a Load Conversion file is required to provide load models.

Use generator capability curves = True | False False When True is specified, generator reactive power limits are computed from data specified in the Generator Capability file (in this case, a Generator Capability file must be provided). When False is specified, they remain fixed as specified in the powerflow data.

Powerflow Control Parameters The value of the following poweflow control parameters must be one of these keywords: Always | Never | In pre-contingency | In post-contingency Their meaning is clear in most cases. Some comments are provided for further clarification. Identifier Default Limit generator VArs = . . . Always Limit swing bus generator VArs = . . . Always With the Always option, the reactive power from the swing generator will be limited to its maximum and minimum (QMAX and QMIN) defined in the powerflow data, even though the active power from the swing generator is not limited to its PMAX and PMIN. Remote control by generators = . . . Always

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With the Always option, remote control by generators in pre- and post-contingency is according to the powerflow data. With the Never option, the remote controlled buses of generators are ignored. These generators will then control their local bus voltages:

• within their [Vlo, Vhi] specified in the powerflow data if Vhi–Vlo<0.2 pu, or,

• at local bus voltage in the powerflow data, V0, if Vlo<V0<Vhi, else, or,

• at Vhi if V0>Vhi, or at Vlo if V0<Vlo With the In pre-contingency option, remote buses controlled by generators in pre-contingency are done according to the powerflow data. When solving post-contingency powerflow, the remote control is ignored and the generators will control their local bus voltages:

• at pre-contingency voltage, Vp, if Vlo<Vp<Vhi, or,

• at Vhi if Vp>Vhi, or at Vlo if Vp<Vlo The In post-contingency option is not accepted for this parameter. Adjust SVC / continuous switched shunts = . . . Always Adjust discrete switched shunts = . . . Never Adjust ULTCS for voltage control = . . . Never Adjust ULTCS for MVAr flow control = . . . Never Adjust phase-shifters for MW flow control = . . . Never Adjust static tap-changers for voltage control = . . . Never Adjust static tap-changers for MVAr control = . . . Never Adjust static phase-shifters for MW control = . . . Never Adjust static series compensators = . . . Never Adjust area interchanges = . . . Never Area Interchange is not controlled for the base case itself (to avoid shifting the initial system conditions). Instead, after the base case is solved, the values of area exports are computed and the Area Interchange Schedules are set to these values. With each transfer increase step, the Area Interchange Schedules are adjusted by the required increase/decrease in the export of affected areas. When area interchange control is enabled, there are two ways to compute the total loads in an area:

• Add all loads whose buses are assigned to the area. Set Include Load In Area

Interchange Control to False to use this method.

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• Add all loads whose load IDs are assigned to the area. Set Include Load In Area

Interchange Control to True to use this method. Adjust automatic SPS = . . . Never Adjust manual SPS = . . . Never

Powerflow Solution Parameters Identifier Default Convergence tolerance for PF solution = MVA-Tol 1.0 Maximum iterations for PF solution = Max-Itr 50 Maximum iterations for adjustments = Max-Adj-Itr Max-Itr This applies when any of the controls (such as ULTC control) is enabled. After Max-Adj-Itr solution iterations, the controls are frozen at their current positions. Adjustments threshold = Adj-Th 0.01 Controls are adjusted after voltage/angle correction becomes smaller than this threshold. MW threshold for governor and AGC dispatch = DP 10 Low impedance threshold = ZIL 0.0001 Lines with impedance smaller than ZIL are considered as Zero Impedance Lines. Blow up voltage = Max-dV 1.0 Acceleration for PV bus voltage = Acc 0.9 Tolerance for PV bus voltage = V-Tol 0.0001 Shunt voltage band threshold = dV 0.01

In switchable shunt control, the discrete shunts that control the local bus voltage within Vhi-Vlo < dV are first adjusted continuously until they reach desired voltage and then are frozen at the nearest bank size. Otherwise, the banks of these shunts are switched in and out one at a time. FDPF solution method = Mthd 1 When Mthd is 1, the XB version of the fast decoupled powerflow method is used and when it is 2, the BX version is used.

Flow Check Parameters Identifier Default

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Line rating no. = Rl 1 Post-contingency line rating no. = Rcl Rl Transformer rating no. = Rt Rl When Rl (Rt) is between 1 and 6, line (transformer) ratings 1, 2, …, or 6 in the powerflow data are used. When Rl (Rt) is zero, line (transformer) flows are not checked or reported. When Rl (Rt) is -1, the ratings specified in the Rating file are used The above ratings apply to both pre- and post-contingency, unless post-contingency ratings are specified. Post-contingency transformer rating no. = Rct Rt

Rl, Rt, Rcl and Rct must either all be between 1 and 6 (inclusive), or all be between -1 and 0 (inclusive).

Threshold for flow check = Fth 100.0 When Check Branch Flows (in Functions parameters) is True, flows that are above Fth % of the specified ratings are considered as overloads (security violation). This threshold applies to both pre- and post-contingency, unless post-contingency threshold is specified. Threshold for post-contingency flow check = Fcth Fth Exclude branches below kV level = Bkv 0.0 If the base kV of a branch from-bus or to-bus is less than Bkv, that branch is not included in overload check and flow report. Merge branch rating file with PF ratings = True | False False If True, and if all rating numbers specified (Rl, Rt, Rcl and Rct) are positive, then the branch rating file is read. The ratings included in the branch rating file and the ratings in the powerflow data are combined and used. The ratings in the branch rating file take precedence over the ratings in the powerflow data. If a branch in the branch rating file is not among the area, zone, and bus subsystem specified using the Include Branches Of parameters, it will not be checked for overloads. Include branches of area = area-list Include branches of zone = zone-list Include branches of bus = bus-list When all rating numbers specified (Rl, Rt, Rcl and Rct) are positive, flows of branches only in area, zone and bus subsystem specified by area-list, zone-list, and bus-list are checked and reported. Refer to Section 8.1.4 on the rules for entering data lists. Several records can be included with different data lists.

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When all rating numbers specified (Rl, Rt, Rcl and Rct) are negative, these Include records are ignored and the branches included in the branch ratings file are checked and reported for overloads. PF Report Parameters Identifier Default Report bus information = True | False False Report generator information = True | False False Report AGC information = True | False False Report interface flows = True | False False Report circuit flows = True | False False Interfaces and circuits must be defined in the Interface and Circuit file. Report branch flows = True | False False The list of branches must be specified by the Include Branch records described in Flow

Check parameters (or by the Ratings file). Report DC network solutions = Full | Converters | None None When Full is specified, DC converter information (modes, angles, etc.) and DC flows are reported. When Converters is specified, only DC converter information is reported. When None is specified, there will be no DC report. Report adjusted switchable shunts = True | False False Report VAR-limited generator information = True | False False Report area interchange information = True | False False Report adjusted transformers for voltage control = True | False False Report transformers for flow control = True | False False Report static tap-changers/phase-shifters = True | False False Report series compensators = True | False False Report Range Parameters The parameters in this category allow specification of an area, zone, and bus subsystem to which the PF Report options specified will be applied:

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Include area = area-list Include zone = zone-list Include bus = bus-list Refer to Section 8.1.4 on the rules for entering data lists. Several records can be included with different data lists. If no data is specified, the entire system is assumed.

Zone Report Parameters The parameters in this category allow specification of two zone lists for reporting zone information: Report summary of zone = zone-list

Generation, load, shunt, etc. information will be reported for the specified zone-list. Report losses of zone = zone-list Loss will be reported for the specified zone-list. Refer to Section 8.1.4 on the rules for entering zone-lists. Several records can be included with different zone-list.

Miscellaneous Parameters Identifier Default Name Option = No | Name | Name (allow duplicates) | Equipment Name No

When No is specified, buses, zones, and areas in all data files in the VSAT case are specified by their numbers. Other components (generator, load, line, etc.) are specified by bus numbers and IDs. When Name is specified, buses, zones, and areas in all data files in the VSAT case are specified by their names and VSAT stops if it finds duplicate bus names in the case. Other components are specified by bus names and IDs. When Name (allow duplicates) is specified, VSAT continues even if it finds duplicate bus names in the case. If a duplicate bus name is used in a data file, the actual bus used by VSAT will be randomly selected. When Equipment Name is specified, a power system component (bus, generator, load, line, etc.) is specified by a 32-character Equipment Names. Zones and areas are specified by the 16-character names. To use this option, the powerflow data must include equipment names for all components. This parameter must appear before any data record containing bus (zone, area) name or equipment name. Ignore missing buses, branches, etc. = True | False False

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When True is specified and if a bus (branch, etc.) specified in Transfer, Contingency or any other data file is not found in the powerflow data, VSAT gives a notice and ignores the missing bus. When False is specified and if the same situation occurs, VSAT gives an error and stops the run. Fix generator Pmin, Pmax, BaseMVA = True | False False When True is specified and if Pmin (Pmax, Base MVA) of a generator in Transfer, AGC or any other data file is not acceptable, VSAT gives a notice and fixes the data (uses a default value). When False is specified and if the same situation occurs, VSAT gives an error and stops the run. Flat Start = True | False False When True is specified, the base powerflow case is solved starting from flat voltages and open generator VAR limits. Show ULTC adjustments during PF solution = True | False True Respect Generator Coupling = True | False False When True is specified, the generation of Combined Cycle Power Plant (CCPP) units is redistributed and is dispatched in a special mode in the transfer analysis according to rules defined in a Generator Coupling File.

Voltage correction tolerance for base case = Vb-Tol 1.0 When VSAT solves the base powerflow case, if the voltages are shifted by more than Vb-Tol from their initial value in the unsolved powerflow data, the case will be rejected. To accept the case and continue, set Vb-Tol to a large number. Post-Contingency Island Bus Count Threshold = Nbisl 0 Islands with fewer buses than Nbisl, without HVDC converters, and without a swing bus are outaged in post-contingency solution, regardless of generation dispatch for contingency option.

Output Volume = Vol 1 When Vol is 0, the progress file will contain the input descriptions and minimum information. When Vol is 1, the progress file will include the description of transfer increases, contingencies, and powerflow solutions. When Vol >1, more detailed information is printed in the progress file. Save Powerflow = At Last Case | At Point Pnt, Contingency Ctg, Before Stress | At Point Pnt, Contingency Ctg, After Stress | At Source Xmw, Contingency Ctg, Before stress |

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At Source Xmw, Contingency Ctg, After stress | No No When At Last Case is specified, the powerflow data of the last case in the VSAT solution process is saved in the “scenario_id”.psn file in PFB format. Note: (a) this case may be unsolved; (b) if contingencies are applied, this case may correspond to a post-contingency condition. When At Point is specified, the powerflow data of Point number Pnt of transfer increase/decrease is saved. Point 1 is the base point, Point 2 is the second point (after one step increase), etc., as seen in the VSAT messages and progress report. If Pnt is zero or negative, this record is ignored. When At Source is specified, the powerflow data is saved when “Source X” of the transfer reaches Xmw. This option is not accepted for 2-dimensional transfers. For 1-dimensional transfers Xmw must be within 1 MW of the source value at a transfer point. For example, if Source X changes from 500 to 600 to 700, etc., Xmw=500 indicates the first point, Xmw=600 indicates the second point, etc. Xmw=605 will be ignored since it is not within 1 MW of a transfer point. If “Transfer analysis = No”, the value of Xmw is unimportant and the powerflow data is saved at the base point. When At Point or At Source is specified, the powerflow data of contingency Ctg is saved. Ctg is the contingency name (enclosed in single quotes) or contingency number (sequential number of “Run” and “Must Run” contingencies). When Ctg is specified as ‘Pre-contg’ or 0, it indicates the pre-contingency case (at specified Point or Source value). When Before

Stress is specified, the powerflow data is saved at the specified transfer point and contingency before applying the stress (Margin). When After Stress is specified, the powerflow data is saved after applying the stress at the specified point. When No is specified, the powerflow data is not saved. At Last Case, At Point and At Source must be typed with one space between the words. There can be any number of spaces (with or without one comma) between the other words on the right side of the “=” sign.

Custom Parameters Identifier Default Include Negative Loads In Transfer Limit = True | False False When True is specified, the amount of negative load in source groups in the base powerflow is reported in the transfer limit file. The negative loads are not scaled during transfer, however. If False, the amounts are not reported, and the load is not scaled. Include Slack Generation in Transfer Limit = True | False False When True is specified, the generation at slack buses is included in the source/sink report (note that slacks cannot participate in the source/sink increase/decrease). Perform both ULTC enable/disable computations = True | False False

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When True is specified, two powerflow solutions will be performed for each contingency (and at each transfer point if applicable). In the first solution, VSAT freezes all voltage control ULTC actions and reports any violations. If this solution is voltage stable (i.e., a powerflow solution is found), VSAT will perform the second powerflow solution in which UTLC actions are based on the user selections defined in the Powerflow Control

Parameters and Control Mode File described below. Also, when True is specified, Permissible Voltage Change Difference in Percent should be provided (default is = 6). The %Delta-V limit defined in the Criteria file will be reduced by this value to check post-contingency voltage decline/rise in the first powerflow solution (i.e. with all ULTC frozen). For example, when Permissible Voltage Change Difference in Percent is set to 6, and the allowed post-contingency voltage decline and rise of a bus is defined in the Criteria file as 10% and 12% respectively. Then the allowed post-contingency voltage decline and rise of this bus in the second powerflow solution will be 10% and 12% respectively. In the first powerflow solution, however, the allowed post-contingency voltage decline and rise of this bus will be set to 4% and 6% respectively. Use CPF to Trace PV Curve = At Stability Limit | No No When At Stability Limit is specified, Continuation Powerflow (CPF) will be performed from any pre-contingency and post-contingency voltage stability limiting point (where fast decoupled method cannot solve the powerflow anymore and stops tracing the PV curve) to keep tracing the PV curve. There are some assumptions when performing CPF:

(1) The stress direction will keep the same as the last step of the transfer of the current PV curve.

(2) Discrete controls will be disabled; they will be frozen at their status at the voltage stability limit.

(3) Pmax and Pmin limits of generators will be ignored. The PV curve computed using CPF will be plotted together with the PV curve computed using fast decoupled method. However, the voltage stability limit found by fast decoupled method will still be reported. When Modal Analysis option is also set as At Stability Limit, modal analysis

will be performed at the critical point found by CPF.

8.5 Transfer File

This file describes the transfer definition in terms of load and/or generation increase or decrease in the system. It is needed in a scenario where stability (or security) limit computation is requested in the Parameter file. Two types of transfers can be specified: One-dimensional involving a source (X) and a sink (D), and Two-dimensional involving three sources/sinks (X, Y and D). X and Y are also referred to as independent

variables and D as dependent variable.

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The security limit(s) of a 1-D transfer is computed step by step. In each step, X and D are increased or decreased by the same amount. For example, to find the security limit of transferring power from generators in area A (X) to load in area B (D), area A generation may be increased by steps of 100 MW and in each step area B load is increased by the same amount. To find the security limit of transferring power from generators in area A to generators in area C, area A generation may be increased by steps of 50 MW and in each step area C generation is decreased by the same amount. The security region of a 2-D transfer is computed in radial direction, each starting from the base point. In each direction, X, Y and/or D is increased or decreased step by step similar to a 1-D transfer limit computation. For example, if X and Y are generation and D is load, in the 45o direction, in each step, X and Y may be increased by 50 MW and D is increased by 100 MW. In the -45o direction, in each step, X may be increased by 100 MW, Y is decreased by 100 MW and D remains constant.

Each source and sink can be defined as any combination of groups including

• Load scale. In such a group, MW loads at all included buses are scaled up or down by the required amount in a dispatch step. The MVAR loads are adjusted according to the Scale Load command specified in this group.

• Generation scale. In such a group, MW generation of all included generators is scaled up or down by the required amount in a dispatch step. The distribution of MW dispatch among the generators in the group may be by MW Output or by MW Reserve. In this generation dispatch mode, neither a generator can be outaged when its power is reduced to zero, nor can an out-of-service generator be put in service to participate in generation dispatch. During generation scaling, the output limits (Pmax and Pmin) specified in the powerflow data are respected. Within a generation scale group, when a generator reaches its output limit, other generators take up its share.

• Generation schedule. In such a group, MW generation of all included generators is scaled up or down by the order specified in the group for the required amount in a dispatch step. In this generation dispatch mode, a generator can be outaged when its power is reduced to zero; alternatively, an out-of-service generator can be put in service to participate in generation dispatch. During generation scheduling, the output limits (Pmax and Pmin) specified in the powerflow data are also respected, but they can be changed in the data.

• Merit order dispatch of generation. In such a group, generators participating in the dispatch are allocated in different blocks and MW generation of these generators is scaled up or down by the order specified for the block for the required amount in a dispatch step, up to the specified limit (Pl and Ph). In this generation dispatch mode, a generator can be outaged when its power is reduced to zero; alternatively, an out-of-service generator can be put in service to participate in generation dispatch. During generation dispatch, the output limits (Pmax and Pmin) specified in the powerflow data are also respected, but they can be changed in the data.

• DC converter share. A fixed share of the transfer can be assigned to specified DC links.

• Phase shifter share. A fixed share of the transfer can be assigned to specified phase shifters. Each group must consist of different loads, generation (each load or generating unit cannot belong to more than one group), DC links, or phase shifters. Each group has a specified Share and Order, which must be positive. When the groups are dispatched by Order, the group with smallest Order is dispatched first, and when it reaches the maximum (or minimum) the second group is dispatched, and so on, until the last group reaches maximum (or minimum), the

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specified transfer increase (or decrease) limit is reached, or security limit is reached. If two or more groups have the same Order, they are dispatched in the order that they appear in the data. When the groups are dispatched by Share, all groups of the source are dispatched together. Their Share determines what percentage of load/generation increase/decrease is assigned to each group. Once one group reaches maximum or minimum, transfer increase/decrease stops (other groups will not take up the share of limited group, even if they are not at their limit). The sum of Shares of all groups belonging to each source/sink doesn’t have to be 100 since VSAT scales them to 100%. There is a special mode in dispatch by Share. If a source or sink consists of only generation scale groups where two or more such groups are defined, and if dispatch share of each group is set to zero, then, VSAT automatically computes the share of each group based on the group active power spinning reserve obtained in the base powerflow data. This ensures that generation in all groups will reach maximum or minimum simultaneously. Example 1

Assume that the source X of a transfer consists of: (1) One generation scale group, with Share=15 and Order=2, consisting of generators A and B. (2) One generation schedule group, with Share=25 and Order=1, consisting of generators C and D. (3) One generation scale group, with Share=10 and Order=1, consisting of generators E and F. Then for a 100 MW increase in X, with dispatch option “By Share” the three groups are dispatched together as follows: (1) Generation of A and B will be scaled up (proportional to their initial MW output if scale option is

set to “MW Output”, otherwise, proportional to their MW reserve if scale option is set to “MW Reserve”) by 30 MW.

(2) Generation of C and D will be increased (in the order specified for each unit) by 50 MW. (3) Generation of E and F will be scaled up (proportional to their initial MW output if scale option is

set to “MW Output”, otherwise, proportional to their MW reserve if scale option is set to “MW Reserve”) by 20 MW

With dispatch option “By Order”, for any increase in X, generation of C and D will be increased first, and after they reach their maximum, generation of E and F will be increased, and finally when they reach their maximum, generation of A and B will be increased. Example 2

Assume that the source X of a transfer consists of: (1) One generation scale group, with Share=0, consisting of generators A and B. Assume further that in

the powerflow the total MW reserve for generators A and B is 200 MW. (2) One generation scale group, with Share=0, consisting of generators C and D. Assume further that in

the powerflow the total MW reserve for generators C and D is 300 MW. Then for a 100 MW increase in X, with dispatch option “By Share” the two groups are dispatched together as follows:

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(1) Generation of A and B will be scaled up (proportional to their initial MW output if scale option is

set to “MW Output”, otherwise, proportional to their MW reserve if scale option is set to “MW Reserve”) by 40 MW.

(2) Generation of C and D will be scaled up (proportional to their initial MW output if scale option is

set to “MW Output”, otherwise, proportional to their MW reserve if scale option is set to “MW Reserve”) by 60 MW

The first record in a transfer file must be: [VSAT 9.x Transfer] Optional description record(s) can be included in the file as: {Description} line 1 of description line 2 of description … {End description} A 16-character name is specified for the transfer by: Transfer name = ’name' The step sizes for transfer increase or decrease are specified by: Step size = MW-Step-1 Cutoff step size = MW-Step-2 Transfer increase or decrease starts with MW-Step-1. If a limit is found and if MW-Step-2 is specified, a fine-tuning process is started to determine the limit within the threshold of MW-Step-2. The user can specify the ranges of MW flows on certain interfaces using the following records: Limit on interface = 'interface-name1’, Infmin1, Infmax1 Limit on interface = 'interface-name2’, Infmin2, Infmax2 Limit on interface = 'interface-name3’, Infmin3, Infmax3 . . . . . .

Infmin and Infmax are the upper and lower limits of the pre-contingency MW flow on the interface

respectively. Once any of the limits is reached, the transfer stops. Balance Loss by Source D = True | False When True is specified, the loss changes during the dispatch will be balanced by Source D instead of the swing bus. By default, the setting is False. For 2-D transfers, the radials to be searched on the X-Y plane are specified by: From Angle = fr-ang

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To Angle = to-ang Number of Radials = Nrd The angles are specified in degrees, with respect to the X axis. By default, fr-ang is 0, to-ang is 360 and Nrd is 16. The source X in a transfer is defined by a group of records starting with: {Source X} A 16-character name for this source is specified by: Source name = 'name' The increase and decrease limits for this source are specified by: Decrease limit = MW-decrease Increase limit = MW-increase For 1-D transfers:

(1) When MW-decrease = 0 and MW-increase > 0, Source X will increase (and Source D will

decrease or increase depending on whether both X and D are generation, both are load, or one is generation and one is load) until the security limit is found or until X reaches the increase limit of MW-increase.

(2) When MW-decrease > 0 and MW-increase = 0, Source X will decrease until the security limit is

found or until X reaches the decrease limit of MW-decrease. (3) When MW-decrease > 0 and MW-increase > 0, if the base case (before changing the transfer) is

found to be secure, MW-decrease is ignored and the situation will be the same as (1) above. If the base case is insecure, the transfer will be reversed and Source X will decrease until a secure point is found or until X reaches the decrease limit of MW-decrease which means a secure point is not found. If the secure point is found, the results tell how much the transfer (Source X) should be reduced to make an insecure base operating condition secure. This is different from (2) above where the base case is secure and the results tell how much Source X can decrease and still remain secure.

The direction of increase and decrease is determined as follows: (1) When the source contains generation groups only, increasing this source means increasing the

generations of this source. (2) When the source contains load groups only, increasing this source means increasing the load of this

source. (3) When the source contains both generation groups and load groups. The direction depends on which

group appears first in the data. If a generation group appears first, increasing this source means increasing the generations and decreasing the loads of this source. If a load group appears first, increasing this source means increasing the loads and decreasing the generations of this source.

Dispatch option of this source is specified by:

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Dispatch groups = by share or Dispatch groups = by order

Following the above records, one or more groups of load scaling or generation scaling/scheduling belonging to this source, and DC converters participating in the transfer, are defined as follows. A group of loads to be scaled up/down is defined by: {Load scale group} Following the above record, the share and order of this group for the increase/decrease of this source is specified by: Group share = Psh Group order = Ord Psh must be greater than 0. Default share is 100. Ord must be greater than 0. Default order is 1. One the following options can be specified for load scaling: Scale load = P and Q Scale load = P only Scale load = Lag PF PwrFctr Scale load = Lead PF PwrFctr With P and Q option, the load at each bus in this group is scaled with fixed power factor (i.e., the load power factor remains constant at each bus). This is the default option. With P only option, only the MW load is scaled and MVAR load is kept constant. With Lag PF option, the load in this group is scaled with the specified lagging power factor PwrFctr (greater than 0, smaller than or equal to 1), i.e., New_Load = Old_Load + Delta_Load, where Delta_Load has the lagging power factor PwrFctr. With Lead PF option, the load in this group is scaled with the specified leading power factor PwrFctr (greater than 0, smaller than or equal to 1). The loads belonging to this group are specified by any combination of (see Section 8.1.4 for rules on entering the data): Include area = area-list

Include zone = zone-list

Include bus = bus-list

Include load = bus ‘id’

Exclude area = area-list

Exclude zone = zone-list

Exclude bus = bus-list

Exclude load = bus ‘id’

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The negative (and zero) loads included in the group do not participate in dispatch but may be reported by setting appropriate option in the Parameter file. The non-scalable loads (refer to PSAT User Manual for details) included in the group do not participate in dispatch. The load scaling group definition ends with the record: {End Load scale group} A group of generators to be scaled up/down is defined by: {Generation scale group} Following the above record, the share and order of this group for the increase/decrease of this source is specified by: Group share = Psh Group order = Ord

Psh must be greater than 0. Default share is 100. Ord must be greater than 0. Default order is 1. The generation scale option of this group is specified by: Scale Generation = MW Output or Scale Generation = MW Reserve When generation scale option is set to MW Output (default), MW output increase/decrease of generators in this group will be allocated in proportion to their initial MW output. If generation scale option is set to MW Reserve, MW output increase/decrease of generators in this group will be allocated in proportion to their MW reserve. The generation belonging to this group is specified by any combination of (see Section 8.1.4 for rules on entering the data): Include area = area-list



Include kV = kV-list Include generator = bus 'id' Exclude area = area-list



Exclude kV = kV-list Exclude generator = bus 'id'

The out-of-service units and units with negative and zero output included in this group do not participate in dispatch but may be reported by setting appropriate option in the Parameter file. Also, units with output

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outside its limits (Pmin and Pmax specified in the powerflow data) are excluded. The generation scaling group definition ends with the record: {End Generation scale group} A group of generators to be scheduled is defined by: {Generation schedule group} Following the above record, the share and order of this group for the increase/decrease of this source is specified by: Group share = Psh Group order = Ord

Psh must be greater than 0. Default share is 100. Ord must be greater than 0. Default order is 1. The generators belonging to this group are specified in an ordered list. Each generator record in this list contains: Bus-no ’id’ up-order dn-order on-off Pmax Pmin bus-no and id identify the generator. up-order specifies the order of this generator for increasing the generation. If unit A has a lower up-order than unit B, generation of A is increased to its Pmax before B is increased. If both units have the same up-order and unit A is specified in the list before unit B, then generation of A is increased before B. If up-order is zero, the generation of the unit is not increased. Default is 1. dn-order specifies the order of this generator for decreasing the generation. If unit A has a lower dn-order than unit B, generation of A is decreased after the generation of B is decreased to its Pmin. If both units have the same dn-order and unit A is specified in the list before unit B, then generation of A is decreased after B. If dn-order is zero, the generation of the unit is not decreased. Default is 1. If on-off is 1, the unit is turned off when its generation is reduced to zero. Pmin must be zero for those units with on-off flag of 1. Default is 0. Pmax and Pmin specify the maximum and minimum generation for this unit. If -1 (or by default), the limits in the powerflow data are used. Out-of-service units can be included in the list and they will be dispatched as long as their Pmin is set to 0. However, a unit with a status of -1 (indicating that the unit is out of service and unavailable, see PSAT User Manual for details) will not be dispatched. The generation scheduling group definition ends with the record: {End Generation schedule group} Merit Order Dispatch consists of a sequence generation block groups. A Merit Order Dispatch group is defined by

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{Merit order dispatch group} Following the above record, the share and order of this group for the increase/decrease of this source is specified by: Group share = Psh Group order = Ord Psh must be greater than 0. Default share is 100. Ord must be greater than 0. Default order is 1. The generation block groups belonging to this dispatch group are specified in an ordered list. Each generation block group starts with the following record: {Generation block group} The generation scale option of this block is specified by: Scale Generation = MW Output or Scale Generation = MW Reserve The block may also be given a descriptive name. This name is not required to be unique, and it is not used for other purpose. Block Name = 'Name'

For each generator in the block, a record in specified as follows: Bus-no ’id’ on-off pl ph Bus-no and id identify the generator. on-off is either 0 or 1. If on-off is 1, the unit is turned off when its generation is reduced to zero. Default for on-off is 0. Pl and Ph specify the starting point and ending point for the MW output of this generator in this generation block. If these are set to -1 (default), Pmin and Pmax in the powerflow data will be used for Pl and Ph respectively. If Pl and/or Ph are outside of Pmin and Pmax in the powerflow data, Pmin and Pmax will be set to Pl and/or Ph specified. Out-of-service units can be included in the list and they will be dispatched as long as their on-off parameter is set to 1. However, a unit with a status of -1 (indicating that the unit is out of service and unavailable, see PSAT User Manual for details) will not be dispatched. The generation blocks in one group will be scaled by output or reserve to Ph. The generation block group definition ends with the record: {End Generation block group} If generation block group A is specified in the list before generation block group B, then generation of A is increased before B and decreased after B.

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A generator can only belong to one merit order dispatch group. A generator can only be specified in a generation block group once. When the generation of a generation block group is being adjusted but the current generation of a generator in this group is not between Pl and Ph, the generator will not be adjusted. The merit order dispatch definition ends with the record: {End Merit order dispatch group} Each DC converter participating in the transfer from/to this source is defined by the following group of records starting with: {DC converter} The converter is specified by: Converter name = 'DC-Bus1' 'DC-Bus2' AC-Bus 'Ckt' DC-Bus1, DC-Bus2, AC-Bus and Ckt are the converter DC bus names, AC bus number (or name) and circuit-id as in the powerflow (PFB) data. The converter voltage is specified by: Converter voltage = Vdc Vdc is the converter nominal DC voltage (kV). It is needed if the converter mode includes ID (otherwise, it is ignored). Participation factor = Fper-cent

Fper-cent is the increase (>0) or decrease (<0) in MW flow (PA setpoint) of the converter as a percentage of increase in this source. If the converter mode does not include PA, the current (ID) setpoint will be increased by

Fper-cent × 0.01× dX /Vdc, where dX is the increase (decrease) in this source. If the DC participation is not specified (or Fper-cent is zero), any increase/decrease in this source must find a path through other AC (or DC) branches. If there are no AC branches for this flow, Fper-cent of the converter (or sum of them if there are several converters) must be set to 100 (if converter flow must increase for increase in this source) or -100 (otherwise). The DC converter participation definition ends with the record: {End DC converter} The share of the transfer for each phase-shifter that is controlling the flow from/to this source is specified by:

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Phase Shifter Participation = From-Bus To-Bus 'id' Fper-cent From-Bus, To-Bus and id are the phase-shifter terminal bus numbers (or names) and circuit ID as in the powerflow data. The order of From-Bus and To-Bus is important (could be the reverse of the phase-shifter’s From and To buses in the powerflow data). Fper-cent is the change in scheduled MW flow of the phase-shifter as a percentage of increase in this source. This is positive if the flow in the direction of From-Bus to To-Bus (as specified above) must increase for the increase in this source. When the phase-shifter participation is not specified (or Fper-cent is zero), if phase-shifters control the flows in powerflow solutions, any increase/decrease in this source must find a path through other branches (flow through the phase-shifter remains constant until the phase-shift angle reaches the limit). But if phase-shifter control is disabled, this record has no effect (phase-shift angle is fixed and transfer increase distributes among all available paths). When there are no other paths to this source except phase-shifter(s), Fper-cent (their sum if there are several phase-shifters) must be set to 100 or -100 depending on the direction of From-Bus and To-Bus. After all groups (load, generation, DC converters, phase shifters) belonging to this source are specified, its definition ends with the record: {End Source X} The transfer sink (source) D is defined with a similar group of records, starting and ending with: {Source D} {End Source D} Between these records, the decrease and increase limits of this source and load scale, generation scale and generation schedule groups, and DC converters belonging to this source are specified in the same way as for the source X. For a 2-D transfer, the source Y is defined similarly, starting and ending with: {Source Y} {End Source Y} The end of the entire transfer data definition is specified by record: [End] Examples

In the following example, the source X is defined as generation scaling in Zone 5 and 6, and source D is defined as load scaling in Area 1. The actual transfer analysis will be performed as follows:

• If the system condition in the base powerflow is secure, the generation in source X will be increased, up to 800 MW. This is matched with the load increase in Area 1. The computation is stopped before

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source X increase reaches 800 MW, if a security violation is found for the base system condition or under any post-contingency condition. In this case, the security (stability) limit is at the highest transfer level without any security violation. If source X can be increased to 800 MW without any security violation, the security (stability) limit is more than 800 MW.

• If the system condition in the base powerflow is insecure, the generation in source X will be decreased, up to 500 MW. This is matched with the load decrease in Area 1. The computation is stopped before source X decrease reaches 500 MW, if all security violations are cleared for the base system condition and for all post-contingency conditions. In this case, the security (stability) limit is at the last (lowest) transfer level. If source X is decreased to 500 MW and there is still security violation(s), the security (stability) limit is more than a decrease of 500 MW in source X.

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The next example shows a 2-D transfer definition:

• The source X is defined as generation scaling in Zone 5 and 6, in the range of 500 MW decrease and 800 MW increase.

• The source Y is defined as generation scaling in Zone 4, in the range of 500 MW decrease and 700 MW increase.

• The source D is defined as load scaling in Area 1. The amount to be scaled is to match the generation scaling in source X and Y.

The transfer analysis is to be performed at radial directions from the base system condition on the X-Y plane from 0 degrees (X axis) to 360 degrees (X-axis again), at an interval of 30 degrees going counterclock-wise, as shown in the figure. The dispatch ranges for source X and source Y will be as specified in the data. The dispatch for source D will be made as

[VSAT 9.0 Transfer] {Description} Transfer from East-generation to Area 1 load {End Description} Transfer Name = 'East Gen ' Step Size = 100 Cutoff Step Size = 20 {Source X} Source Name = 'EAST GEN' Decrease Limit = 500 Increase Limit = 800 {Generation Scale Group} Group share = 100 Include Zone = 5 Include Zone = 6 {End Generation Scale Group} {End Source X} {Source D} Source Name = 'A 1 LOAD' Decrease Limit = 9999 Increase Limit = 9999 {Load Scale Group} Group share = 100 Scale Load = P and Q Include Area = 1 {End Load Scale Group} {End Source D} [End]

Source X

Source Y

Base system condition

Transfer change

direction at 30°

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required from dispatches of source X and Y. The final result will usually be a 2-D region around the base system condition showing the secure operation region. Figure 1.3 shows such a secure region display.

[VSAT 9.0 Transfer] {Description} 2-D Transfer: East-vs-North generation, against Area 1 load {End Description} Transfer Name = 'E vs N Gen' Step Size = 100 Cutoff Step Size = 20 From Angle = 0 To Angle = 360 Number of Radials = 12 {Source X} Source Name = 'East Gen' Decrease Limit = 500 Increase Limit = 800 Dispatch Groups = By Share {Generation Scale Group} Group Share = 100 Scale Generation = MW Output Include Zone = 5 Include Zone = 6 {End Generation Scale Group} {End Source X} {Source Y} Source Name = 'North Gen' Decrease Limit = 500 Increase Limit = 700 Dispatch Groups = By Share {Generation Scale Group} Group Share = 100 Scale Generation = MW Output Include Zone = 4 {End Generation Scale Group} {End Source Y} {Source D} Source Name = 'Area 1 Load' Decrease Limit = 9999 Increase Limit = 9999 Dispatch Groups = By Share {Load Scale Group} Group Share = 100 Scale Load = P and Q Include Area = 1 {End Load Scale Group} {End Source D} [End]

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8.6 Criteria File

This file contains the voltage limit and VAr reserve criteria. For voltage limit criteria, the buses to be checked can be included in several groups and different voltage limit criteria can be defined for each group. Similarly, several groups of reactive power sources can be specified and a different VAr reserve limit criterion can be defined for each group. If a Criteria file is not specified for a scenario, there won't be any voltage limit or VAr reserve criteria applied for that scenario. The first record in this file must be: [VSAT 9.x Criteria] Optional description record(s) can be included in the file as: {Description} line 1 of description line 2 of description … {End description} Also, an optional 16-character identifier can be specified for the criteria data by: Criteria name = ’Identifier' Each voltage limit group starts with the following record: {Voltage limit} The limits on voltage magnitude for this group are specified by: High limit = Vhi Low limit = Vlo Vhi and Vlo are in p.u. The limits can be applied to either pre-contingency voltages, or post-contingency voltages, or both by specifying one of the following records: Apply in = Pre-contingency or Apply in = Post-contingency or Apply in = Pre and post-contingency Pre and post-contingency is the default.

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The bus voltages belonging to this group are specified by any combination of (see Section 8.1.4 on rules of entering the data): Include area = area-list



Include kV = kV-list




Exclude kV = kV-list

The voltage limit group definition ends with record: {End Voltage limit} Limits for post-contingency voltage decline/rise with respect to pre-contingency voltage (i.e., | Pre-contingency voltage - Post-contingency voltage |) are specified by delta-V groups and/or % delta-V groups. Each delta-V limit group definition starts with the following record: {Delta-V limit} The limits on voltage decline/rise are specified by: Decline limit = dVdec Rise limit = dVinc dVdec and dVinc are in p.u. The bus voltages belonging to this group are specified by any combination of: Include area = area-list








The delta-V limit group definition ends with record: {End Delta-V limit} Each %delta-V limit group definition starts with the following record: {%Delta-V limit} The limits on voltage decline/rise are specified by:

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Decline limit = dVdec Rise limit = dVinc dVdec and dVinc are in percent of the pre-contingency voltages (e.g. if a bus has pre-contingency voltage of 1.045 p.u. and dVdec is 10%, the allowable Delat-V change in p.u. is 0.1045). The bus voltages belonging to this group are specified by any combination of: Include area = area-list








The %delta-V limit group definition ends with record: {End %Delta-V limit} Each VAr reserve group starts with the following record: {VAr reserve limit} The reserve limit for this group is specified by one of the following records: Reserve limit = Xres MVAr or Reserve limit = Xpc % Xres is the limit for the sum of MVAR reactive reserves of all specified sources in this group. Note that Xres can be either positive or negative. When it is positive, the reserve is compared with the maximum and when it is negative the reserve is compared with the minimum. For example, if a generator has (Qmin, Qmax) = (100, 200) MVAR. Xres = 40 MVAr means that the generator must operate with Q in the range of (100, 160) MVar. Xres = -40 MVAr means that the generator must operate with Q in the range of (140, 200) MVar.

Xpc is the limit for the sum of reactive reserves of all specified sources in this group as a percentage of their existing MVAr output. There must be a space or comma before MVAr or %. The limits can be applied to either pre-contingency, or post-contingency, or both by specifying one of the following records: Apply in = Pre-contingency or

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Apply in = Post-contingency or Apply in = Pre and post-contingency Pre and post-contingency is the default. The VAr sources belonging to this group are specified by any combination of: Include sources of area = area-list

Include sources of zone = zone-list

Include sources of bus = bus-list

Include sources of kV = kV-list

Exclude sources of area = area-list

Exclude sources of zone = zone-list

Exclude sources of bus = bus-list

Exclude sources of kV = kV-list

sources in the above records must be replaced by one of the following: generators (as in Include generators of area = 2) variable shunts (as in Include variable shunts of bus = 30) frozen shunts (as in Include frozen shunts of zone = 400) Same rules apply to these records as the Include/Exclude records described in Section 8.1.4 The VAr reserve limit group definition ends with record: {End VAr reserve limit} The end of the Criteria data is specified by record: [End] Example

The following criteria file defines these security criteria:

• Post-contingency voltages at all buses in area 2 must be within 0.8 and 1.2 pu.

• Post-contingency voltage decline at all buses in area 1 must be within 0.08 pu.

• Each of zone 4, 5 must have at least 12% reactive power reserve. Note that in addition to the above, three other security criteria are available:

• Voltage stability: this is violated if a powerflow case cannot be solved. This is always enabled in VSAT.

• Voltage stability margin: this is defined in the margin file.

• Overload: this is defined in parameter file with optional data from the branch rating file.

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8.7 Margin File

Beside the voltage limit and VAr reserve criteria specified in the Criteria file, a voltage stability margin criterion can be specified in a Margin file. If a Margin file is not specified for a scenario, there won't be any voltage stability (VS) margin criterion for that scenario. An operating point is voltage secure (i.e., inside the secure range/region) if its distance to voltage instability is greater than the specified margin. This means that the operating point must remain stable (i.e. powerflow solutions exist for all contingencies) when it is moved (stressed) in the direction of, and by the amount of, the specified margin. For example, the margin can be specified as 200 MW load and generation increase (uniform scaling) in area A, or it can be specified as 100 MVAr reactive load increase in area X. The margin can be specified as any combination of groups of (active or reactive) load and generation changes. It can be partly or completely independent of the direction of the transfer. For example, if the transfer is from generation in area A to load in area B, the first margin defined above is partly in the direction of the transfer while the second margin is independent of the transfer.

The first record in this file must be:

[VSAT 9.0 Criteria] {Description} Post-contingency voltage limit in area 2 Voltage decline limit in area 1 Q reserve in each of zones 4, 5 {End Description} Criteria name = 'Sample Criteria' {Voltage limit} High limit = 1.2 Low limit = 0.8 Apply in = Post-Contingency Include area = 2 {End Voltage limit} {Delta-V limit} Decline limit = 0.08 Rise limit = 0.99 Include area = 1 {End Delta-V limit} {VAr reserve limit} Reserve limit = 12 % Apply in = Pre and post-contingency Include generators of zone = 4 {End VAr reserve limit} {VAr reserve limit} Reserve limit = 12 % Apply in = Pre and post-contingency Include generators of zone = 5 {End VAr reserve limit} [End]

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[VSAT 5.x Margin] Optional description record(s) can be included in the file as: {Description} line 1 of description line 2 of description … {End description} Also, an optional 16-character identifier can be specified for the margin data by: Margin name = ’Identifier' The margin can be specified as one or more load and/or generation scale groups. Each load scale group starts with the following records: {Load scale group}

The loads belonging to this group are specified by any combination of (see Section 8.1.4 on rules of entering the data): Include area = area-list



Include load = bus ‘id’




Exclude load = bus ‘id’

One the following options can be specified for load scaling: Scale load = P and Q Scale load = P only Scale load = Q only Scale load = Lag PF PwrFctr Scale load = Lead PF PwrFctr With P and Q option, the load at each bus in this group is scaled with fixed power factor (i.e., the load power factor remains constant at each bus). This is the default option. With P only option, only the active load is scaled and reactive load is kept constant. With Q only option, only the reactive load is scaled and active load is kept constant. With Lag PF option, the load in this group is scaled with the specified lagging power factor PwrFctr (greater than 0, smaller than or equal to 1), i.e., New_Load = Old_Load + Delta_Load, where Delta_Load has lagging power factor PwrFctr. With Lead PF option, the load in this group is scaled with the specified leading power factor PwrFctr (greater than 0, smaller then or equal to 1).

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The size of load increase in this group is specified by: Increase by = Xpc % or Increase by = Xinc MW (or MVAr) When % is specified, active and/or reactive load of this group is increased by Xpc% of the existing load. Otherwise, with the P only (P and Q) option, the active load is increased by Xinc MW (and reactive load is increased with constant power factor), and with the Q only option the reactive load is increased by Xinc MVAr. There must be a space or comma before %, MW or MVAr. All the non-zero loads in the group are scaled up (or down if increase value is negative) uniformly. If there is no load in the group, equal loads will be added at all buses to the sum of specified Xinc MW or MVAr. The load scale group ends with the record: {End Load scale group} Each generation scale group starts with the following records: {Generation scale group} The generation belonging to this group is specified by any combination of (see Section 8.1.4 for details): Include area = area-list




Include generator = bus 'id' Exclude area = area-list




Exclude generator = bus 'id' The size of generation increase in this group is specified by: Increase by = Xpc % or Increase by = Xinc MW When % is specified, MW generation of this group is increased by Xpc% of the existing generation. Otherwise, it is increased by Xinc MW. There must be a space or comma before % or MW.

VSAT Users Manual



All units with non-zero generation in the group are scaled up (or down) uniformly, while their Pmax (Pmin) is ignored. If all in-service units in the group have zero MW output, their generation is increased proportional to their MVA rating to the sum of Xinc MW. If there are no in-service units in the group, all off-line units are switched on and dispatched in proportion to their MVA rating (e.g., to bring in an off-line unit, define one group with only this unit included). The generation scale group ends with the record: {End Generation scale group} The amount of Xinc MW or Xpc % for one load/generation group can be specified as zero. In this case the MW change for this slack group will be determined from the total MW change of all other groups to balance the net load/generation increase in the system. Optionally, a dispatch option can be specified to balance the load/generation/losses after the operating point is moved by the above Xinc / Xpc amounts (with or without a slack group) by one of the following records: Dispatch option = Governor Response or Dispatch option = AGC Action or Dispatch option = None None is the default. The end of the margin data is specified by record: [End] Example

The following margin file defines a voltage stability margin of 200 MW load and generation increase in area 1. Thus, if a transfer is to be performed, every step calculated for the transfer (both pre- and post-contingency) must meet this margin requirement.

VSAT Users Manual



8.8 Monitored Variable File

This file specifies the variables that will be monitored during the computations.

The first record in this file must be: [VSAT 7.x Monitored Variable] Optional description record(s) can be included in the file as: {Description} line 1 of description line 2 of description … {End description} Also, an optional 16-character identifier can be specified for the monitor data by: Monitor name = ’Identifier' Available variables can be monitored by any combination of the following records:

pu Voltage of bus = bus-list kV Voltage of bus = bus-list

Voltage (in pu or kV) of buses included in the bus-list (a list or range of bus numbers or names, similar to the Include Bus record described in Section 8.1.4) will be monitored MW generation of bus = bus-list

[VSAT 9.0 Margin] {Description} 200 MW load/gen increase in area 1 {End description} Margin name = 'Sample Margin' {Load scale group} Scale load = P and Q Increase by = 200 MW Include area = 1 {End Load scale group} {Generation scale group} Increase by = 200 MW Include area = 1 {End Generation scale group} [End]

VSAT Users Manual



MW output of generators at buses in the bus-list will be monitored. Generation at each bus in the list (not the sum of generation at all buses) will be monitored and reported separately. If equipment name option is used to identify generators, a generator name can be entered in this command. MVAr generation of bus = bus-list

MVAr output of generators at buses in the bus-list will be monitored, similar to monitoring MW generation at buses described above. MVAr reserve of bus = bus-list

Positive MVAr reserve of generators of buses in the bus-list will be monitored, similar to monitoring MW generation at buses described above. The generation of a group of units is monitored by any combination of the following records: {MW Generation} Group name = 'MW-Gr-name' Include area = area-list Include zone = zone-list Include bus = bus-list Include unit = bus 'id'

Exclude area = area-list Exclude zone = zone-list Exclude bus = bus-list

Exclude unit = bus 'id'

{End MW Generation} Sum of MW generation of a group of units defined by the Include and Exclude records will be monitored. Same rules apply to these records as the Include/Exclude records described in Section 8.1.4. bus and id in Include/Exclude Unit record specify the bus number and ID of one unit. MW-Gr-name is a 16-character name given to this group. If blank (default), the group name is set to the name of the bus of one of the units in the group. {MVAr Generation} Group name = 'MVAr-Gr-name' Include area = area-list Include zone = zone-list Include bus = bus-list Include unit = bus 'id'


Exclude unit = bus 'id'

{End MVAr Generation} Sum of MVAr generation of a group of units defined by the Include and Exclude records will be monitored, similar to monitoring MW generation of a group of units described above. {MVAr Reserve} Group name = 'MVAr-Rs-name'

VSAT Users Manual



Include area = area-list Include zone = zone-list Include bus = bus-list Include unit = bus 'id'


Exclude unit = bus 'id {End MVAr Reserve}

Sum of positive MVAr reserve of a group of units defined by the Include and Exclude records will be monitored, similar to monitoring MW generation of a group of units described above. Other MVAr reserves are monitored by any combination of the following records: MVAr reserve of zone = zone-list Positive MVAr reserve of generators of zones in the zone-list will be monitored. Reserve of each zone in the list (not the sum of all zones) will be monitored and reported separately. Criteria MVAr reserves = Yes (or No)

MVAr reserves of all Q-Criteria groups (defined in the Criteria file) will be monitored if Yes is specified. If No is specified (or by default) these are not monitored (but still checked for violation).

To monitor MVAr reserves in different parts of the system without imposing any limits on those reserves, you can define them as Q-Criteria groups with zero MVAr-reserve criteria in the Criteria file. The flows and losses of interfaces and circuits are monitored by any combination of the following records: MW flow of interface = 'interface-name1’, 'interface-name2’, . . . MVAr flow of interface = 'interface-name1’, 'interface-name2’, . . . MW loss of interface = 'interface-name1’, 'interface-name2’, . . . MVAr loss of interface = 'interface-name1’, 'interface-name2’, . . . MW/MVAr flows or losses of specified interfaces will be monitored. MW/MVAr flows are the sum of powers at the metered-end of interface branches, in the direction of from-bus to to-bus, as defined in the Interface and Circuit file. interface-name1, etc., must be separated by commas. MW flow of circuit = 'circuit-name1’, 'circuit-name2’, . . . MVAr flow of circuit = 'circuit-name1’, 'circuit-name2’, . . . MVA flow of circuit = 'circuit-name1’, 'circuit-name2’, . . . AMP flow of circuit = 'circuit-name1’, 'circuit-name2’, . . . MW/MVAr/MVA/AMP flows of specified circuits will be monitored. Flows are monitored at the metered-end of the first branch of the circuit, in the direction of from-bus to to-bus, as defined in the Interface and Circuit file. circuit-name1, etc., must be separated by commas.

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{MW Load} Group name = 'MW-Load-name' Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV1:kV2 Include bus type = bus-type Include load = bus 'id' Exclude area = area-list Exclude zone = zone-list Exclude bus = bus-list

Exclude kV = kV1:kV2 Exclude bus type = bus-type Exclude load = bus 'id' {End MW Load}

Sum of MW load of a group of loads defined by the Include and Exclude records will be monitored. {MVAr Load} Group name = 'MVAr-Load-name' Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV1:kV2 Include bus type = bus-type Include load = bus 'id' Exclude area = area-list Exclude zone = zone-list Exclude bus = bus-list

Exclude kV = kV1:kV2 Exclude bus type = bus-type Exclude load = bus 'id' {End MVAr Load}

Sum of MVAr load of a group of loads defined by the Include and Exclude records will be monitored. {MW Loss} Group name = 'MW-Loss-name' Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV1:kV2 Include bus type = bus-type Include branch = from-bus to-bus 'ckt-id' Include 3W-transformer = prim-bus sec-bus ter-bus 'ckt-id' Exclude area = area-list Exclude zone = zone-list Exclude bus = bus-list

Exclude kV = kV1:kV2 Exclude bus type = bus-type Exclude branch = from-bus to-bus 'ckt-id' Exclude 3W-transformer = prim-bus sec-bus ter-bus 'ckt-id'

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{End MW Loss}

Sum of MW loss of a subsystem defined by the Include and Exclude records will be monitored. {MVAr Loss} Group name = 'MVAr-Loss-name' Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV1:kV2 Include bus type = bus-type Include branch = from-bus to-bus 'ckt-id' Include 3W-transformer = prim-bus sec-bus ter-bus 'ckt-id' Exclude area = area-list Exclude zone = zone-list Exclude bus = bus-list

Exclude kV = kV1:kV2 Exclude bus type = bus-type Exclude branch = from-bus to-bus 'ckt-id' Exclude 3W-transformer = prim-bus sec-bus ter-bus 'ckt-id' {End MVAr Loss}

Sum of MVAr loss of a subsystem defined by the Include and Exclude records will be monitored. {MW Load+Loss} Group name = 'MW-Load+Loss-name' Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV1:kV2 Include bus type = bus-type Include load = bus 'id' Include branch = from-bus to-bus 'ckt-id' Include 3W-transformer = prim-bus sec-bus ter-bus 'ckt-id' Exclude area = area-list Exclude zone = zone-list Exclude bus = bus-list

Exclude kV = kV1:kV2 Exclude bus type = bus-type Exclude load = bus 'id' Exclude branch = from-bus to-bus 'ckt-id' Exclude 3W-transformer = prim-bus sec-bus ter-bus 'ckt-id' {End MW Load+Loss}

Sum of MW load and loss of a subsystem defined by the Include and Exclude records will be monitored. {MVAr Load+Loss} Group name = 'MW-Load+Loss-name' Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV1:kV2

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Include bus type = bus-type Include load = bus 'id' Include branch = from-bus to-bus 'ckt-id' Include 3W-transformer = prim-bus sec-bus ter-bus 'ckt-id' Exclude area = area-list Exclude zone = zone-list Exclude bus = bus-list

Exclude kV = kV1:kV2 Exclude bus type = bus-type Exclude load = bus 'id' Exclude branch = from-bus to-bus 'ckt-id' Exclude 3W-transformer = prim-bus sec-bus ter-bus 'ckt-id' {End MVAr Load+Loss}

Sum of MVAr load and loss of a subsystem defined by the Include and Exclude records will be monitored. {MVAr Shunt} Group name = 'MVAr-Shunt-name' Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV1:kV2 Include bus type = bus-type Include fixed shunt = bus 'id' Include switched shunt = bus 'id' Exclude area = area-list Exclude zone = zone-list Exclude bus = bus-list

Exclude kV = kV1:kV2 Exclude bus type = bus-type Exclude fixed shunt = bus 'id' Exclude switched shunt = bus 'id' Exclude all fixed shunt Exclude all switched shunt {End MVAr Shunt}

Sum of MVAr Shunt of a group (at nominal voltage) of shunts defined by the Include and Exclude records will be monitored. {MVAr Shunt Actual} Group name = 'MVAr-Shunt-name' Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV1:kV2 Include bus type = bus-type Include fixed shunt = bus 'id' Include switched shunt = bus 'id' Exclude area = area-list Exclude zone = zone-list Exclude bus = bus-list

Exclude kV = kV1:kV2

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Exclude bus type = bus-type Exclude fixed shunt = bus 'id' Exclude switched shunt = bus 'id' Exclude all fixed shunt Exclude all switched shunt {End MVAr Shunt}

Sum of MVAr Shunt of a group (at actual voltage) of shunts defined by the Include and Exclude records will be monitored. MW flow of branch = from-bus to-bus 'ckt-id'

MW flow of this branch will be monitored. The branch flow is computed in the direction of from-bus to to-bus as defined in this file. The flow is computed at the from-bus side, unless the to-bus is specified as the metered-end by specifying it as a negative number (in case of the bus name option, a minus sign must be added before the to-bus-name inside the single quote, for example, ‘frombusname’ ‘-tobusname’ ‘C1’). MVAr flow of branch = from-bus to-bus 'ckt-id'

MVAr flow of this branch will be monitored, similar to monitoring MW flow of a branch described above. MW flow of 3W-transformer =

prim-bus sec-bus ter-bus 'ckt-id' 'winding' 'quantity-name'

MW flow of this winding will be monitored. winding can be PRI, SEC or TER. The flow will be computed in the direction of flow into the transformer, unless a minus sign is added before the winding inside the single quote, for example, ‘-PRI’. quantity-name is for identifying the flow in the output, it is a string of up to 32 characters, if left empty, default quantity name will be assigned. MVAr flow of 3W-transformer =

prim-bus sec-bus ter-bus 'ckt-id' 'winding' 'quantity-name'

MVAr flow of this winding will be monitored, similar to monitoring MW flow of a winding of a three winding transformer described above. Tap of 2W-transformer = from-bus to-bus 'ckt-id' 'tap-name'

Tap ratio of this transformer will be monitored. In the case of a phase shifter, phase shift angle will be monitored. tap-name is for identifying the tap in the output, it is a string of up to 32 characters, if left empty, default tap name will be assigned. Tap of 3W-transformer =

prim-bus sec-bus ter-bus 'ckt-id' 'winding' 'tap-name' 'tap-type'

tap-type can be Ratio, Angle or left blank. When it is left blank, the quantity to be monitored will

be chosen depends on the control type of the winding, i.e., tap ratio of voltage and MVAr control winding, phase shift angle for MW control winding. Status of Generator = bus 'id' 'quantity-name'

Status of Switched Shunt = bus 'id' 'quantity-name'

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Status of branch = from-bus to-bus 'ckt-id' 'quantity-name' Status of 3w-transformer =

prim-bus sec-bus ter-bus 'ckt-id' 'quantity-name' Status of this equipment will be monitored. quantity-name is for identifying the quantity in the output, it is a string of up to 32 characters, if left empty, default quantity name will be assigned. Inter Area MW Flow = Area1

Total MW export from Area1 will be monitored.

Inter Area MW Flow = Area1, Area2

MW export from Area1 to Area2 will be monitored.

Inter Area MVAr Flow = Area1

Total MVAr export from Area1 will be monitored.

Inter Area MVAr Flow = Area1, Area2

MVAr export from Area1 to Area2 will be monitored.

The end of the monitored variable data is specified by record: [End]

Example

The following monitored variable file monitors:

• Voltages at buses between 100 and 300, and at buses 500, 501, 502.

• MW and MVAR flow on interfaces ‘NORT-CEN’ and ‘EAST-CEN’ which are defined in the interface and circuit file.

• MVAR reserve of all Q groups defined in the criteria file.

[VSAT 9.0 Monitored Variable] {Description} Monitor bus voltages, interface flows, and Criteria reactive reserves {End description} Monitor name = 'Sample Monitoring' Voltage of bus = 100:300 Voltage of bus = 500, 501, 502 MW flow of interface = 'NORT-CEN', 'EAST-CEN' MVAr flow of interface = 'NORT-CEN', 'EAST-CEN' Criteria MVAr reserves = Yes [END]

VSAT Users Manual



8.9 Contingency Script File

Contingency script file contains the description of contingency types and is used to create the full-set or screened contingency file in VSAT. For example, it can contain script to create all N-1 circuit outage contingencies in one area. It may contain several contingency groups. Each group specifies the required types of contingencies.. The first record in the file must be: [VSAT 4.x Contingency Script]

Each contingency group must begin with the following record: {Contingency Group} and end with: {End Contingency Group} Within the contingency group, one or more types of outages are specified by subgroups described below. Note that areas, zones, and buses must be specified by Number, even if another component identification method is specified in the Parameter file. The contingencies created by VSAT would be in terms of number, name, or equipment name depending on the component identification method selected. The rules of Include and Exclude records described Section 8.1.4 apply to this data file. Single branch (transmission line or transformer) outage subgroup is specified by: {Outage Branch} Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV-list Include Branch = from-bus to-bus 'cct id'


Exclude kV = kV-list Exclude Branch = from-bus to-bus 'cct id'

{End Outage Branch} Double branch outage subgroup is specified by: {Outage Double Circuit} Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV-list

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Exclude kV = kV-list {End Outage Double Circuit} This subgroup creates double outages of all parallel branches (those with the same from-bus and to-bus) in the specified region (areas, zones, buses, kV). Single three-winding transformer outage subgroup is specified by: {Outage 3W-Transformer} Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV-list Exclude area = area-list Exclude zone = zone-list Exclude bus = bus-list

Exclude kV = kV-list {End Outage 3W-Transformer} Single generator outage subgroup is specified by: {Outage Generator} Include area = area-list Include zone = zone-list Include bus = bus-list Include MVA = MVA-list Exclude area = area-list Exclude zone = zone-list Exclude bus = bus-list

Exclude MVA = MVA-list {End Outage Generator} Single fixed-shunt outage subgroup is specified by: {Remove Fixed Shunt} Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV-list Exclude area = area-list Exclude zone = zone-list Exclude bus = bus-list

Exclude kV = kV-list {End Remove Fixed Shunt} The contingency script data ends with optional record: [End]

VSAT Users Manual



This data may contain one or more contingency groups, and each of these groups may contain one or more outage subgroups. For example, if a contingency group contains only one generator outage subgroup, it results in single generator contingencies. If another group contains two single branch outage subgroups, it results in double branch contingencies, including all combinations of branches in the first subgroup and those in the second subgroup. Example

The following example contains the script to create N-1 branch outages in area 1.

8.10 Contingency File

A contingency file contains the description of contingencies to be ranked by the Contingency Screening module or to be evaluated by the Security Assessment module. A Contingency file specified in a Scenario file is required by the Security Computation module if in the Parameter file Contingency Analysis is set to True. A full-set Contingency file specified in a Scenario file is required by the Contingency Screening module to create the Contingency file. The first record in this file must be: [VSAT 9.x Contingency] Each contingency is specified by a group of records starting with: {Contingency} or {Contingency Must Run} or {Contingency Don't Run} The Don’t-Run contingencies are ignored by Contingency Screening and Security Assessment modules. The Must-Run contingencies are always selected by the Contingency Screening module, while the others are screened. In the Security Assessment module, the Must-Run contingencies are treated the same as the others.

A unique 32-character name must be specified for each contingency using the command:

[VSAT 9.0 Contingency Script] {Contingency Group} {Outage Branch} Include area = 1 {End Outage Branch} {End Contingency Group} [End]

VSAT Users Manual



Contingency name = 'name' Outage, connection, and control of bus, branch, and transformer can be made using the following commands: Outage Bus = bus-number

Outage Branch = from-bus-number to-bus-number 'cct id'

Connect Branch = from-bus-number to-bus-number 'cct id'

Open One End of Branch = from-bus-number to-bus-number 'cct id'

Outage 3W-Transformer = prim-bus-no. sec-bus-no. ter-bus-no. 'cct id'

Connect 3W-Transformer = prim-bus-no. sec-bus-no. ter-bus-no. 'cct id' Lock 2W Transformer = from-bus-number to-bus-number 'cct id' Lock 3W Transformer = prim-bus-no. sec-bus-no. ter-bus-no. 'cct id' Note:

• An outaged bus cannot be put in service.

• Outage Branch and Connect Branch commands can be used for transmission circuits and two-winding transformers.

• Open One End of Branch can only be used for transmission circuits.

• An Open One End of Branch command opens the to-bus (as specified in the contingency file) end of the branch.

• To connect a branch or three-winding transformer, all of its terminal buses must be in-service.

• When a two-winding or three-winding transformer is “locked”, all of its taps are frozen in the post-contingency powerflow solution.

• Default cct id is 1. Status of the three-winding transformer can be changed using the following command: Change 3W-Transformer Status = prim-bus sec-bus ter-bus 'id' Status

Status is an integer between 0 to 4, refer PSAT User Manual for details. Generation changes can be made using the following commands: Change Generation = bus-number 'gen-id' new-MW

Scale Generation in Zone = zone-number Pup%

Note:

• Default gen-id is 1. If new-MW >0, the generator is put in service (if it was out of service) and its output is set at new-MW. If new-MW =0 (default), generator is outaged (to keep it in service, set new-MW to 0.01).

VSAT Users Manual



• For the Scale Generation in Zone command, MW generation of units in the zone are scaled by 1 + Pup%/100, while their MW limits are ignored.

Load changes can be made using the following commands: Shed Load = bus-number drop-MW drop-MVAR model-number

Shed Load % = bus-number dP dQ

Change Load = bus-number 'id' new-MW new-MVAr

Scale Load in Zone = zone-number Pup% Qup%

Note:

• For the Shed Load command, the active and reactive load (of model-number type) at the bus are reduced by drop-MW and drop-MVAR, respectively.

model-number = -1: constant PQ (default) -2: constant current -3: constant impedance >0: voltage dependent load model defined in the powerflow file or Load

Conversion file

Load Conversion must be requested in the Parameter file if model-number other than -1 is specified in this data

• For the Shed Load % command, the active and reactive load (all components/models) at the bus is reduced by dP% and dQ%, respectively.

• For the Change Load command, the active and reactive load at the bus with ID id is changed to new-MW and new-MVAr, respectively.

• For the Scale Load in Zone command, MW loads in the zone are scaled by 1 + Pup%/100 and MVAR loads are scaled by 1 + Qup%/100.

Shunt changes can be made using the following commands: Remove Fixed Shunt = bus-number drop-MVAR

Change Fixed Shunt = bus-number 'sh-id' new-MVAr

Turn on Switched Shunt = bus-number 'sh-id'

Turn off Switched Shunt = bus-number 'sh-id'

Note:

• For the Remove Fixed Shunt command, the shunt at the bus is reduced by drop-MVAR (at nominal voltage). So, to drop 50 MVAR capacitor at the bus, set drop-MVAR to 50.

• For the Change Fixed Shunt command, the shunt at the bus with ID sh-id is changed to new-

MVAR (at nominal voltage).

• For the Turn on Switched Shunt command, the shunt at the bus is turned on with the admittance value that it had in the powerflow data or when it was last turned off in a previous case.

• For the Turn off Switched Shunt command, the shunt at the bus is turned off (taken out-of-service).

VSAT Users Manual



• Default sh-id is ‘ ’ (blank). Change of DC converter control mode can be made using the commands: Change DC Converter = 'Bus1' 'Bus2' AC-Bus 'Ckt' 'new-Mode' s1 s2 [s3]

Note:

• Bus1, Bus2, AC-Bus, and Ckt specify the converter by its DC buses, AC bus, and circuit ID as in the powerflow data.

• new-Mode is the new Control Mode (4 characters for regular converters and 6 characters for voltage-sourced converters). Refer to PSAT user manual for a complete description of DC converter control mode.

• s1, s2 and s3 are the new first, second and third setpoints (for regular converters, only s1 and s2 are required). Refer to PSAT user manual for a complete description of DC converter control setpoints.

In a contingency, it is possible to scale generation, load, and shunt in a subsystem. Use the following commands to achieve these. {Scale MW Generation in Subsystem} Subsystem Name = 'ss-name' Include Area = area-list Include Zone = zone-list Include Bus = bus-list Include kV = kV-list Include Generator = bus-number 'id' Exclude Area = area-list Exclude Zone = zone-list Exclude Bus = bus-list Exclude kV = kV-list Exclude Generator = bus-number 'id' Scale By = Pup% | Scale To = new-MW Respect Pmax and Pmin = True | False Exclude Neg Gen = True | False Outage Generator when Pgen Equal Zero = True | False {End Scale MW Generation in Subsystem} {Scale Load in Subsystem} Subsystem Name = 'ss-name' Include Area = area-list Include Zone = zone-list Include Bus = bus-list Include kV = kV-list Include Load = bus-number 'id' Exclude Area = area-list Exclude Zone = zone-list Exclude Bus = bus-list Exclude kV = kV-list Exclude Load = bus-number 'id'

VSAT Users Manual



Scale MW By = Pup% | Scale MW To = new-MW Scale MVAr By = Qup% | Scale MVAr To = new-MVar | Keep Power Factors Const | Keep MVar Const

Exclude Neg Load = True | False {End Scale Load in Subsystem} {Scale Fixed Shunt in Subsystem} Subsystem Name = 'ss-name' Include Area = area-list Include Zone = zone-list Include Bus = bus-list Include kV = kV-list Include Fixed Shunt = bus-number 'id' Exclude Area = area-list Exclude Zone = zone-list Exclude Bus = bus-list Exclude kV = kV-list Exclude Fixed Shunt = bus-number 'id' Scale Conductance By = Pup% | Scale Conductance To = new-MW Scale Capacitance By = Qup% | Scale Capacitance To = new-MVar Scale Inductance By = Qup% | Scale Inductance To = new-MVar {End Scale Fixed Shunt in Subsystem} Note:

• In the above, the default for all True or False options is True.

• Scale To keyword is used to express the change in physical unit (e.g. MW or MVAr). Scale By keyword is used to express the percent change.

• In both Scale Capacitance To and Scale Inductance To command, positive new-MVar means capacitive.

• Non-scalable load will not be changed (refer to PSAT User Manual for details). There are several special commands that can be used in a contingency: 1. Run a PSAT macro: Run PSAT Macro File = 'PSAT_macro_name.psm' VSAT will only execute the relevant commands in a PSAT macro. For example, some PSAT Macro commands such as changing single-line-diagram does not apply to VSAT and thus will not be executed. 2. Split a bus: {Bus Splitting} Split Bus = spbus-num Move Branch to New Bus = spbus-num, xxx, 'id1' Move Branch to New Bus = yyy, spbus-num, 'id2' Move 3W-Transformer to New Bus = xxx, spbus-num, yyy, 'id3' Move Load to New Bus = 'id' Move Generator to New Bus = 'id'

VSAT Users Manual



Move Fixed Shunt to New Bus = 'id' Move Switched Shunt to New Bus = 'id' {End Bus Splitting} When a bus is split, VSAT automatically assigns a bus number to the new bus section. Then, the components connected to the original bus can be moved to the new bus section. 3. Handle SPS model: Apply SPS Models = True | False When “False” is specified, all SPS model will be ignored. The default is True. The end of the specifications for a contingency is indicated by the record: {End contingency} The end of the contingency data is specified by record: [End] Examples

The following example contains two contingencies, one N-1 and one N-2 circuit outages. The following example contains a contingency in which

• Bus 100 is outaged.

• Generator at bus 101 ID ‘1’ is outaged.

• Switched shunt at bus 200 is turned off.

[VSAT 9.0 CONTINGENCY] {Contingency} Contingency name = 'N-1' Outage Branch = 1544 5512 '1' {End contingency} {Contingency} Contingency name = 'N-2’ Outage Branch = 501 5512 '1' Outage Branch = 503 5511 '1' {End contingency} [END]

[VSAT 9.0 Contingency] {Contingency} Contingency name = 'Component Outage' Outage Bus = 100 Change Generation = 101 '1' 0 Turn off Switched Shunt = 200 , , {End contingency} [End]

VSAT Users Manual



The following example contains a contingency with bus splitting:

• Bus 100 is split; a new bus is created.

• The branches 100-101-1 and 105-100-1 are now connected at the new bus.

• Other branches and components connected at bus 100 will still be connected at the bus.

8.11 Contingency Screening Parameter File

This file contains the parameters for contingency screening. Refer to Section 2.8.1 for description and use of these parameters. If this file is not specified in the Scenario file, all parameters take their default values. The first record in this file must be: [VSAT 7.x Contingency Screening Parameter] The screening parameters are specified on separate records, as follows. The contingency screening method is specified by the command: Contingency selection = By number or Contingency selection = By margin If By number is specified, the first screening method is used. If By margin is specified, the second method is used. Default method is By number. For the first screening method, the number of contingencies (Nc, including all the “Must-Run” contingencies) to be selected from the full set of contingencies can be specified by the following command:

[VSAT 9.0 Contingency] {Contingency} Contingency name = 'Bus Splitting' {Bus Splitting} Split Bus = 100 Move Branch to New Bus = 100 101 ‘1’ Move Branch to New Bus = 105 100 ‘1’

{End Bus Splitting} {End contingency} [End]

VSAT Users Manual



Number of contingencies to be selected = Nc The default for Nc is 20. For the second screening method, contingencies with small VS margin can be screened from the full set of contingencies by one of the following commands: Select contingencies within margin = X MW or Select contingencies within margin = x % All the “Must-Run” contingencies and those “To-Be-Screened” contingencies whose VS margin is less than X MW (or x %) are selected from the full-set contingency file and written to the Screened Contingency file. With the % option, x is percentage of the value of source D at the base point. There must be a space or comma before MW or %. The default for X and x is 0. A contingency screening process starts from the determination of the pre-contingency stability limit (nose point of the P-V curve). This is done using the specified transfer definition with two step sizes: Initial step size for PV curve = MW-step-1 Cutoff step size for PV curve = MW-step-2

The transfer is initially increased in steps of MW-step-1 in search of the pre-contingency stability limit. The default for MW-step-1 is the same as the step size specified in the Transfer file. After the system becomes unstable with the last MW-step-1 step, the step size is reduced, in order to reach the nose of the pre-contingency P-V curve, until it becomes smaller than MW-step-2. The default for MW-step-2 is 10.0. After the pre-contingency stability limit is determined, the screening goes through an iterative process to find the transfer level with the desired number of critical contingences. This iteration starts with the first step using the following command: First step size for screening = first-step MW or First step size for screening = pc-first-step %

There must be a space or comma before MW or %. The first point on the pre-contingency P-V curve selected for contingency solution is first-step MW, or pc-first-step % (in terms of the pre-contingency margin) back from the pre-contingency nose point. If neither of the above commands is specified, the default is to use MW step at 10.0 MW. The iteration in search of the desired number of critical contingencies continues to halve the distance between subsequent points on the P-V curve. This process stops if the distance becomes smaller than the threshold set in the following command: Minimum step size for screening = MW-min-step

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or if the number of points on the P-V curve where contingencies are solved exceeds the threshold set in the following command: Maximum number of points for screening = max-points

The default for MW-min-step is 5.0 MW. The default for max-points is 50. In addition to the voltage stability margin, thermal limit can be enforced in contingency screening by using the following command: Check Overload for Screening = True | False

When True is specified, the same thermal ratings as in the security assessment will be used, which is specified in the Parameter file. The default is False. The end of the contingency screening data is specified by record: [End]

Example

The following example contains a set of contingency screening parameters. Defaults are used for the unspecified parameters.

8.12 Interface and Circuit File

This file contains the description of interfaces and circuits. It is needed when the interface and circuit flows should be reported (in the Parameter file) or monitored (in the Monitor file). The first record in this file must be: [VSAT 4.x Interface] Optional description record(s) can be included in the file as: {Description} line 1 of description line 2 of description … {End description}

[VSAT 9.0 Contingency Screening Parameter] Number of contingencies to be selected = 10 Initial step size for PV curve = 100.0 Cutoff step size for PV curve = 5.0 Maximum number of points for screening = 100 [End]

VSAT Users Manual



Interfaces, identified by 16-character names, represent a group of branches (usually parallel lines). Each interface is specified by a group of records as follows: {Interface} Interface name = 'name' Include branch = from-bus1 to-bus1 'cct-id1' Include branch = from-bus2 to-bus2 'cct-id2' . . {End Interface} Circuits, identified by 16-character names, represent a series of branches (usually sections of a tapped transmission line). Each circuit is specified as: {Circuit} Circuit name = 'name' Include branch = from-bus1 to-bus1 'cct-id1' Include branch = from-bus2 to-bus2 'cct-id2' . . {End Circuit} Each branch in the powerflow data has a defined from-bus and to-bus pair. The from-bus and to-bus pairs defined as interface and circuit branches may be in the same bus orders as those in the poweflow data or they may have the reversed bus orders.

The interface flow is the sum of its branch flows. Interface and circuit branch flows are computed in the direction of from-bus to to-bus as defined in this file. The flow is computed at the from-bus side, unless the to-bus is specified as the metered-end by specifying it as a negative number (in case of the bus name option, a minus sign must be added before the to-bus-name inside the single quote, for example, ‘frombusname’ ‘-tobusname’ ‘C1’). The end of the interface and circuit data is specified by record: [End]

Example

The following example contains the definition of one interface and one circuit.

VSAT Users Manual



8.13 Generator Capability File

This file provides data for the following modeling options related to the reactive power capabilities of machines:

• Defining the VAr limits of generators based on the field and armature current limits or reactive power capability curves.

• Changing the fixed VAr limits of generators (to overwrite the limits in the powerflow data).

• Keeping the reactive power output of generators at fixed power factor (for modeling wind turbines with power factor control).

• Defining the PQ characteristics of induction machines (for modeling wind turbines of “Direct Connect Induction Generator” type when their VAr compensation devices are modeled explicitly).

The generator capability file also can specify data which is applied in the post-contingency as well. This file is needed only when Use Generator Capability Curve is set to True in the Parameter file. The first record in this file must be: [VSAT 9.x Generator capability] Optional description record(s) can be included in the file as: {Description} line 1 of description line 2 of description … {End description} This file has up to five data sections: capability data, capability curves, fixed VAr limits, fixed power factors, and induction machine data.

Capability Data Section

[VSAT 9.0 Interface] {Interface} Interface name = 'NORT-CEN' Include branch = 4511 5512 '1' Include branch = 4511 5512 '2' Include branch = 4511 5512 '3' {End Interface} {Circuit} Circuit name = '5L41' Include branch = 1544 5512 '1' {End Circuit} [End]

VSAT Users Manual



During powerflow solutions, VAr limits of generators listed in this section are computed based on their capability data. If the operation of a generator becomes infeasible (cannot be kept inside its capability region), its VAr limits are set to zero without any attempt to reschedule its MW output. The data in this section begins with the record: {Generator capability data} Each generator with capability data is specified on one record as: bus-no 'id' X-syn PF-rt MVA-rt KV-rt Q-erl V-hi V-lo

bus-no (or bus name or generator equipment name), id: identify the generator. X-syn synchronous reactance in pu on MVA-rt and KV-rt base. If 0.0 (or missing), it is set to 2.0 PF-rt rated power factor. If 0.0 (or missing), it is set to 0.85. MVA-rt rated MVA. If 0.0 (or missing), it is set to generator’s base MVA in powerflow data. KV-rt rated KV voltage. If 0.0 (or missing), it is set to generator’s base KV in powerflow data. Q-erl MVAR limit caused by the end-region heating. If 0.0 (or missing), it is set to generator’s

minimum VAr limit (Qmin) in powerflow data. V-hi upper voltage limit in pu. If 0.0 (or missing), it is set to generator’s V-hi in powerflow data. V-lo lower voltage limit in pu. If 0.0 (or missing), it is set to generator’s V-lo in powerflow data. If the armature current limit should be ignored for the generator and only the maximum VAr output should be computed based on the field current limits, add the following command: Ignore armature current limit = Yes If No is specified for this command (the default option), armature current limits are respected for all generators included in this data section. The capability data section ends with the record: {End Generator capability data} Capability Curves Section

During powerflow solutions, VAr limits of generators listed in this section are determined from their capability curves. The data in this section begins with the record: {Generator capability curves}

Generator capabilities are specified by piece-wise linear curves. Each generator may have several curves, each corresponding to one terminal voltage. The following group of records specifies one curve for one generator: {Capability curve} bus-no 'id' Vi P1 Qh1 Ql1 P2 Qh2 Ql2 . . .

VSAT Users Manual



Pn Qhn Qln {End curve} bus-no (or name or generator equipment name) and id identify the generator, Vi is the terminal voltage (pu) for this curve, and Pj (MW), Qhj (MVAr) and Qlj (MVAr) specify the points 1:n on the curve. The order of records in this group is important. Bus-no ‘id’ Vi must be specified on the first record after

{Capability curve} and the points of the curve must be specified in this order: P1 < P2 < … < Pn. Up to 30 points can be specified for each curve. It is possible to specify Qh and Ql for negative P.

All curves of one generator (for different terminal voltages) must be specified after each other before specifying the curves of another generator and they must be specified in increasing order of the terminal voltage (V1<V2<...<Vm). For a given P (generator MW output) and V (terminal voltage), where Vi<V<Vj, VAr limits of the generator are determined by linear interpolation of the ith and jth curves. If V<V1, the limits are computed from the first curve and if V>Vm, the limits are computed from the last curve. If P>Pn of each curve, VAr limits for that voltage are set to zero (without any attempt to reschedule generator’s MW output). The capability curves section ends with the record: {End Generator capability curves}

Fixed VAr Limits Section

The data is this section is used to change the fixed generator VAr limits or voltage control range of generators in powerflow data. The data in this section begins with the record: {Generator fixed limits} Each generator with new fixed limits is specified on one record as: bus-no 'id' Q-max Q-min V-hi V-lo

bus-no (or name or generator equipment name), id: identify the generator. Q-max maximum MVAR limit. Q-min minimum MVAR limit. V-hi upper voltage limit in pu. If 0.0 (or missing), it is set to generator’s V-hi in powerflow data. V-lo lower voltage limit in pu. If 0.0 (or missing), it is set to generator’s V-lo in powerflow data. The fixed limits section ends with the record: {End Generator fixed limits}

Q

P

(P1,Qh1)

(P1,Ql1)

(P2,Qh2)

(P3,Qh3)

(P4,Qh4)

(P2,Ql2)

(P3,Ql3)

V2

V1

(P4,Ql4)

Q

P

(P1,Qh1)

(P1,Ql1)

(P2,Qh2)

(P3,Qh3)

(P4,Qh4)

(P2,Ql2)

(P3,Ql3)

V2

V1

(P4,Ql4)

VSAT Users Manual



Fixed Power Factors Section

Generators specified in this section will operate at fixed power factor (therefore, they will not control any bus voltage). The data in this section begins with the record: {Generator fixed power factors} Each generator with fixed power factor is specified on one record as: bus-no 'id' Q/P

bus-no (or name or generator equipment name), id: identify the generator. Q/P fixed Q/P ratio of the generator (if negative, generator absorbs reactive power). The fixed power factors section ends with the record: {End Generator fixed power factors} Induction Machine Data Section

The MVAr outputs of generators specified in this section will be controlled according to the induction machine characteristic (therefore, they will not control any bus voltage). The data in this section begins with the record: {Induction Machine Data} Each generator modeled as an induction machine is specified on one record as: bus-no 'id' MVA-rt, Rs, Xs, Xm, Rr, Xr

bus-no (or name or generator equipment name), id: identify the induction machine. MVA-rt rated MVA. If 0.0 (or missing), it is set to generator’s base MVA in powerflow data. Rs stator resistance in pu. Xs stator leakage reactance in pu. Xm magnetizing reactance in pu. Rr rotor resistance in pu. Xr rotor leakage reactance in pu. The induction machine section ends with the record: {End Induction Machine Data}

Post-contingency capability data

The format of the post-contingency capability data is the same as above except for the beginning record. Post-contingency data must follow all other normal capability data in the data file. The post-contingency capability data overrides any data entered above in the post-contingency condition. The beginning and end records are as follows: {Generator capability data Post-Contingency} ...

VSAT Users Manual



{End Generator capability data} {Generator capability curves Post-Contingency} ... {End Generator capability curves} {Generator fixed limits Post-Contingency} ... {End Generator fixed limits} {Generator fixed power factors Post-Contingency} ... {End Generator fixed power factors} {Induction Machine Data Post-Contingency} ... {End Induction Machine Data} The end of the generator capability data is specified by record: [End]

Example

The following example contains the definition of a reactive capability curve for a generator.

[VSAT 9.0 Generator capability] {Description} GENERATOR CAPABILITY CURVE {End Description} {Generator capability curves} {Capability curve} 21 '1' 1.0 0.000 168.000 -120.000 60.000 164.000 -116.000 120.000 148.000 -102.000 187.000 116.000 -64.000 212.000 62.000 -62.000 220.000 0.000 0.000 {End curve} {End Generator capability curves} [END]

VSAT Users Manual



8.14 Governor Response File

This file provides data for determining the active power output of generators with governor response to load-generation mismatches caused by contingencies. This file is used when the generation dispatch option specified in the Parameter file is Governor Response. If this file is not provided when Governor

Response is specified as the generation dispatch option, a 4% droop is used for all generators. The first record in this file must be: [VSAT 4.x Governor Response] Optional description record(s) can be included in the file as: {Description} line 1 of description line 2 of description … {End description} The dispatch solution tolerance is specified by the following record: Governor solution tolerance = MW-tol

Governor action stops when the required net dispatch adjustment in an island becomes smaller than MW-

tol. The default for MW-tol is set to 5.0 × powerflow_solution_tolerance. The governors that respond to load-generation mismatches are specified by any combination of: Regulate area = area-list

Regulate zone = zone-list

Regulate bus = bus-list

Do not regulate area = area-list

Do not regulate zone = zone-list

Do not regulate bus = bus-list

The same rules apply to these records as the general Include/Exclude records described in Section 8.1.4. By default, the rest of system not covered by the above data is considered as regulating (therefore, it is sufficient to only specify the region not regulating). The group of records for governor data of generators is specified after the above records. These records begin with: {Governors} Each generator’s governor data in the regulating region is specified on one record as: bus-no 'id' P-hi P-lo R D MVA-bs bus-no (or name or generator equipment), id: identify the generator

P-hi upper limit of MW generation controlled by governor in pu on MVA-bs base. If P-hi ≤0 (or missing), it is set to 0.95.

VSAT Users Manual



P-lo lower limit of MW generation controlled by governor in pu on MVA-bs base. If P-lo ≤0 (or missing), it is set to 0.15.

R regulation in pu on MVA-bs base. If R <0, MW generation is fixed (does not regulate even if it belongs to the regulating region); if R =0 (or missing), it is set to 0.04.

D damping factor in pu on MVA-bs base. If D <0 (or missing), it is set to 0.0.

MVA-bs MVA base of the unit. If MVA-bs ≤0 (or missing), it is set to generator's base MVA in powerflow data

The last generator’s record is followed by: {End Governors} The generators that are not listed in the above data but belong to the regulating region are assigned the following default data: P-hi = 0.95 P-lo = 0.15 R = 0.04 D = 0.0 MVA-bs = generator's base MVA in powerflow data

The governors belonging to the non-regulating region do not regulate even when they appear in the data

with positive regulation (R ≥ 0). Note that if the pre-contingency generation of a unit is outside the limits specified by P-hi and P-lo, it will not be adjusted by the Governor response. Other (regulating) units are

dispatched in proportion to (1/R + D)×MVA-bs, within the limits specified by P-hi and P-lo. The end of the governor response data is specified by record: [End]

Example

The following example contains the definition of governor response data.

8.15 AGC Action File

This file provides data for determining the active power output of generators with AGC response to load-generation mismatches caused by contingencies. The AGC action attempts to keep area interchanges

[VSAT 9.0 Governor Response] Governor solution tolerance = 5.0 Do not regulate area = 1:99 Regulate bus = 2, 3, 4 {Governors} 2 '1' 0.9 0.1 0.05 0.0 800.0 {End Governors} [End]

VSAT Users Manual



within their specified bands under contingencies. This file is needed when the generation dispatch option specified in the Parameter file is AGC Action. The first record in this file must be: [VSAT 7.0 AGC Action] Note that the format of AGC data in this file changed from VSAT version 6 to version 7. Therefore, the version number in the above record must be 7.0 or higher for the format described in this document. However, VSAT is compatible with the old format (6.0 or lower).

Optional description record(s) can be included in the file as: {Description} line 1 of description line 2 of description … {End description} The dispatch solution tolerance is specified by record: AGC solution tolerance = MW-tol

AGC action stops when the required net dispatch adjustment in an area becomes smaller than MW-tol.

The default for MW-tol is set to 5.0 × powerflow_solution_tolerance. The records of AGC data for each area are grouped together and they begin with record: {Area AGC}

The first record in the group specifies the area by its number (or name): Area = area-no

The AGC deadband for this area, in MW, is specified by: Deadband = MW-dbd

There is no AGC action in the area if its initial MW imbalance (area interchange error) is smaller than MW-dbd. The default for MW-dbd is set to max(Int-tol, MW-tol) where Int-tol is the areas interchange tolerance in the powerflow data. The AGC Economic Mode limit for this area, in MW, is specified by: Economic mode limit = MW-ecm

The AGC action in the area is according to the Economic Mode if its initial MW imbalance is larger than MW-dbd and smaller than MW-ecm. In the Economic Mode, all AGC units in the area are dispatched economically (based on their economic data specified below). The default for MW-ecm is set to max(40.0, MW-dbd). The AGC Permissive Mode limit for the area, in MW, is specified by:

VSAT Users Manual



Permissive mode limit = MW-prm

The AGC action in the area is according to the Permissive Mode if its initial MW imbalance is larger than MW-ecm and smaller than MW-prm. In the Permissive Mode, only those AGC units in the area are dispatched (economically) which result in the reduction of MW imbalance, i.e., if net generation has to increase but the output of some expensive units are too high, these units will not be redispatched. The default for MW-prm is set to max(100.0, MW-ecm). The AGC will be in Area Assist Mode if the initial MW imbalance is larger than the Permissive Mode limit. In this mode all AGC units are dispatched according to their loading rates (specified below). The dispatch of AGC units could be either according to one of the AGC modes described above, or according to the specified participation factors, as defined by: Dispatch by participation factors = True | False

When False is specified (default), AGC units are dispatched according to the AGC mode. When True is specified, if the initial MW imbalance is larger than MW-dbd (deadband), all AGC units are dispatched in proportion to their Participation Factors (specified below; within their limits). Dispatch by participation factors is similar to dispatch in the Area Assist Mode where for each unit its

Load_Rate × MVA_base is the Participation Factor. This is done by specifying a different participation factor (based on security, economy, or other considerations) and setting the Dispatch by participation

factors option to True. The AGC units in this area must be specified next. They must follow the record: {AGC units}

Each AGC unit is specified on one record as: bus-no 'id' P-hi P-lo Pfac Ld-Rt MVA-bs Fu-cst X1 Y1 X2 Y2 ... bus-no (or name or generator equipment name), id: identify the generator.

P-hi upper limit of MW generation controlled by AGC in pu on MVA-bs base. If P-hi ≤ 0 (or missing), it is set to 0.95.

P-lo lower limit of MW generation controlled by AGC in pu on MVA-bs base. if P-lo ≤ 0 (or missing), it is set to 0.05.

Pfac generator’s participation factor (for use in the Dispatch by Participation Factors option). If

Pfac ≤ 0 (or missing), this unit will not participate. Ld-Rt generator’s MW loading rate in pu on MVA-bs base per minute (for use in the dispatch in

Area Assist mode). If Ld-Rt ≤ 0 (or missing), it is set to 0.02.

MVA-bs MVA base. If MVA-bs ≤ 0 (or missing), it is set to generator’s base MVA in powerflow data.

Fu-cst fuel cost in $ per MBTU (for use in the dispatch in Economic or Permissive mode). If Fu-cst ≤ 0 (or missing), it is set to 1.0.

VSAT Users Manual



X1 Y1... up to 6 points on generator’s heat rate curve, with X1 in MW and Y1 in BTU per KWhr (for

use in the dispatch in Economic or Permissive mode). If less than 2 points are specified (or no data is provided), 2 pairs of data are selected as: X1=0; Y1=0; X2=MVA-bs; Y2=1.

Note that if the pre-contingency generation of an AGC unit is outside the limits specified by P-hi and P-

lo, it will not be adjusted by AGC action in any mode. Otherwise, it will be dispatched within the limits specified by P-hi and P-lo. The last unit data is followed by record: {End AGC units} The AGC data for this area is terminated by record: {End Area AGC} The Area AGC group of records is repeated for each area with AGC action. The end of the AGC action data is specified by record: [End] Example

The following example contains the definition of AGC action data.

[VSAT 9.0 AGC Action] {Description} Sample AGC action data {End Description} AGC solution tolerance = 5.00 {Area AGC} Area = 1 Deadband = 5.0 Economic mode limit = 5.0 Permissive mode limit = 5.0 {AGC units} 10 ‘1’ 1.0 0.05 0.0 2.74 312.0 0.0 0.0 0.0 312.0 1.0 11 ‘2’ 1.0 0.05 0.0 4.16 200.0 0.0 0.0 0.0 200.0 1.0 20 ‘1’ 1.0 0.05 0.0 4.83 175.0 0.0 0.0 0.0 175.0 1.0 21 ‘2’ 1.0 0.05 0.0 4.83 173.0 0.0 0.0 0.0 173.0 1.0

{End AGC units} {End Area AGC} [END]

VSAT Users Manual



8.16 Load Conversion File

This file specifies how loads are to be converted to voltage dependent models in post-contingency cases. This file is needed when the Convert Load Models option in the Parameter file is set to True or Always

From CLD File. The first record in this file must be: [VSAT 4.x Load Conversion] Optional description record(s) can be included in the file as: {Description} line 1 of description line 2 of description … {End description} The Load Model group of records is used to define load models. This group starts with the following record: {Load models}

Each record in this group defines one load model: model-number A1 A2 A3 N1 N2 N3 B1 B2 B3 M1 M2 M3 Each model is identified with a unique model-number. A load that is converted to a specified load model will have the following model:

P = Load- MW-factor × (A1 VN1 + A2 VN2 + A3 VN3)

Q = Load- MVAR-factor × (B1 VM1 + B2 VM2 + B3 VM3) where V is the voltage magnitude at the load bus and constants Load- MW-factor/Load-MVAR-factor are computed from the specified load (and voltage) in the powerflow data and the percentage specified for this model in the Load Group data (see below). model-number must be a positive integer. The group of load model records ends with: {End load models}

The next set of records define one or more groups of loads and specify how their models are converted (e.g., their active load to be converted to 30% constant impedance, 20% constant current, and 50% constant power; similarly for reactive load). Each group starts with the following record: {Load group}

VSAT Users Manual



Loads belonging to this group are specified by any combination of (see Section 8.1.4 on rules for entering the data): Include area = area-list



Note that Exclude records are not allowed to avoid confusions. To allow flexibilities in specifying load models, multiple load groups can be used. For example, if some loads in an area-list should have a different model, they can remain in this load group and later be included in another load group with the desired model. Each load group specifying new models for its loads overwrites any previous specifications. The load conversion for this group is specified by any combination of the following records: Percentage of constant current load = real-I reactive-I

Percentage of constant impedance load = real-Z reactive-Z

Percentage of load model no. = m1 real-m1 reactive-m1

Percentage of load model no. = m2 real-m2 reactive-m2 . . .

m1, m2, etc., are model-numbers defined by the Load Model group above (or in the base powerflow PFB file). real-I, real-Z, real-m1, …, and reactive-I, rectivel-Z, reactive-m1, … are percentages of active and reactive power at the load buses to be included in the specified models. The remaining load will be modeled as constant power, i.e., Percentage of constant MW load = 100.0 - sum of (real-I + real-Z + real-m1 …) Percentage of constant MVAR load = 100.0 - sum of (reactive-I + rectivel-Z + reactive-m1 …) The number of components with different models (including constant power) for any load must not exceed 5. The load group ends with record: {End load group}

The end of the load conversion data is specified by record: [End] Example

The following example contains the definition of models for the load at bus 5. Assume that this load has 100 MW and 70 MVAR in the powerflow data. The following actual models will be used for load at this bus in VSAT analysis:

• 30 MW of load will be modeled as

25.0

0

25.0

0

09.025.0

V14.0V86.0

)V14.0V86.0(30P

+

+=

VSAT Users Manual



• 10 MW of load will be modeled as

75.0

0

75.0

V

V10P =

• 28 MVAR of load will be modeled as

19.3

0

57.1

0

19.357.1

V23.0V77.0

)V23.0V77.0(28Q

−

−

+

+=

• 14 MVAR of load will be modeled as

5.4

0

5.4

V

V14Q =

• 10 MW and 7 MVAR of load will be modeled as constant current.

• 20 MW and 14 MVAR of load will be modeled as constant impedance.

• The rest 30 MW and 7 MVAR load will be modeled as constant power. In the above, V0 is the voltage at the bus in the base condition.

[VSAT 9.0 LOAD CONVERSION] {Description} Sample load conversion data {End Description} {Load models} 10 0.86 0.14 0.0 0.25 0.09 0.0 0.77 0.23 0.0 1.57 -3.19 0.0 20 1.00 0.00 0.0 0.75 0.00 0.0 1.00 0.00 0.0 4.50 0.00 0.0 {End load models} {Load group} Include bus = 10 Percentage of Constant Current load = 10.0 10.0 Percentage of Constant Impedance load = 20.0 20.0 Percentage of Load Model No. = 10 30.0 40.0 Percentage of Load Model No. = 20 10.0 20.0 {End load group} [End]

VSAT Users Manual



8.17 Load Swap File

This file specifies the bus-pairs for swapping the load. In a contingency, if the first bus in the pair is outaged, all of its loads will be moved to the second bus. The first record in this file must be: [VSAT 7.x Load Swap] Following the above identifier, each bus-pair is specified on one record, so the list will contain two columns of bus numbers, bus names, or node equipment names as in: from-bus to-bus . . . . . . A bus can appear only once as the from-bus (in the first column), while the to-bus can be the same for two or more bus-pairs. Each pair specifies only the load swap from the from-bus to the to-bus. If the load at to-bus should also be swapped when the bus is outaged, it must be specified as the from-bus in another bus-pair, as shown in the example below. The end of the load swap data is specified by record: [End] Example

The following example contains the definition of load swap data. Note that loads at bus 101 will be moved to bus 102 if bus 101 is outaged and loads at bus 102 will be moved to bus 101 if bus 102 is outaged.

8.18 Branch Rating File

This file contains either MVA ratings or Ampere ratings of selected branches. It is needed in a scenario if, in the Parameter file, a negative value is specified for the line/transformer rating number (and overload check or branch report is requested). Note that if a branch rating file is used, all other branch ratings specified in the powerflow are ignored, unless the Merge Branch Rating File With PF Ratings parameter is set to True in the Parameter file. The first record in this file must be:

[VSAT 9.0 Load Swap] 101 102 102 101 133 101 [End]

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[VSAT 4.x Branch Rating] Optional description record(s) can be included in the file as: {Description} line 1 of description line 2 of description … {End description} The rating type is specified by one of the following commands: Rating type = MVA

Rating type = AMP

If MVA is specified (default), the ratings in the file are in MVA. If AMP is specified, the ratings in the file are in Ampere. Following the above records, rating of each line or transformer is specified on one record as: from-bus to-bus 'ckt-id' rating sec-no . . . . . . . . The branch is defined by its from-bus, to-bus, ckt-id, and sec-no, and rating is its MVA or AMP rating indicated by the Rating Type command (in the case of AMP rating, transformer branches are ignored). sec-no is optional and required only for sectional branch. The default for sec-no is 1. For a sectional branch in PFB powerflow data format, all sections have the same from-bus (terminal of the first section), to-bus (terminal of the last section) and ckt-id (id of the sectional branch) and they are distinguished by their sec-no (1, 2, …, in the direction of from-bus to to-bus). After the above records for all lines and two-winding transformers, the MVA or AMP ratings of three-winding transformers, if any, are specified by a group of records as: {3W Transformers} Prim-bus Sec-bus Ter-bus 'ckt-id' Prim-rat Sec-rat Ter-rat . . . . . . . . {End 3W Transformers} The three-winding transformer is defined by its Prim-bus, Sec-bus, Ter-bus, and ckt-id. Prim-rat/Sec-

rat/Ter-rat are its primary/secondary/tertiary MVA or AMP ratings indicated by the Rating Type record. The end of the branch rating data is specified by record: [End] Example

The following example contains the definition of branch rating data.

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8.19 Modal Analysis Parameter File

This file specifies the parameters for Modal Analysis. VSAT reads this file when the Modal Analysis parameter in the Parameter file is set to True. If this file is not specified, VSAT uses default values for all parameters. Modal Analysis is performed at the system condition and contingency as requested in the Parameter file. The first record in this file must be: [VSAT 4.x Modal Analysis Parameter] Each parameter is defined on one record as follows. Number of computed modes = nm nm (default is 1) is the number of modes (the smallest eigenvalues of the reduced Jacobian) to be computed. Print bus participations = Yes | No When Yes is specified (default), bus participations are printed in the output file. When No is specified, bus participations are not printed out. Print left eigenvectors = Yes | No When Yes is specified, left eigenvectors are printed in the output file. When No is specified (default), left eigenvectors are not printed out. Print right eigenvectors = Yes | No

[VSAT 9.0 Branch Rating] {Description} Sample branch rating data {End Description} Rating type = MVA 10 30 '1' 2141.6 1 20 1000 '1' 2141.6 1 20 1000 '2' 2141.6 1 30 2000 '1' 2141.6 1 {3W TRANSFORMERS} 300 3000 310 '1' 500.00 500.00 90.00 300 3000 310 '2' 500.00 500.00 90.00 {End 3W TRANSFORMERS} [End]

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When Yes is specified, right eigenvectors are printed in the output file. When No is specified (default), right eigenvectors are not printed out. Participations / eigenvectors are normalized and sorted with the first (largest) element being 1.0. Maximum number of printed participations = mxp mxp (default is 20) is the maximum number of bus participations and/or eigenvector elements printed for each mode. Minimum value of printed participations = mnp mnp (default is 0.001) is the minimum value of bus participations and/or eigenvector elements printed for each mode. For example, if mxp is 50 and mnp is 0.02, 50 largest participations (and/or eigenvector elements) are printed out if they are all larger than 0.02. Otherwise, only those that are larger than 0.02 are printed out. Number of additional eigenvalues = na

na (default is 2) is the additional eigenvalues to be computed. For numerical accuracy, it is strongly recommended that this parameter be kept at its default value. Complex shift in Jacobian = rj, ij

rj and ij (defaults are 0.0 and 0.0) are real and imaginary parts of a shift value for the Jacobian. Only when necessary for numerical accuracy, non-default values should be specified for these. Tolerance for eigen solution = tol

tol (default is 0.0005) is the tolerance for computed eigenvalues.

Include voltage-dependent loads in Jacobian = Yes | No

When Yes is specified, voltage-dependent loads are included in the Jacobian. When No is specified (default), voltage-dependent loads are not included in the Jacobian. Tolerance for generator Q limit = Qtol Qtol specifies an MVAr tolerance. Those generators that have less than Qtol MVAr reserve (capacitive or inductive) are considered to be at their reactive capability limit. Default is the powerflow solution tolerance specified in the Parameter file. The end of the modal analysis parameters is specified by record: [End]

Example

The following example contains the definition of modal analysis parameters.

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8.20 VQ Curve File

This file specifies the data required for computation of VQ curves. VSAT reads this file when the VQ Curve

Interval parameter in the Parameter file is set to a positive number. Each VQ curve is computed within a specified range of voltage (between Vmin and Vamx) with a specified step size (Vstep). For example, if Vmin=0.8, Vmax=1.1, and Vstep=0.02, The VQ curve will be computed at voltage points 0.8, 0.82, 0.84, …, 1.1 pu.

The first record in this file must be: [VSAT 3.x VQ Curve] The common VQ curves that will be computed for pre-contingency and every post-contingency case are specified by a group of records as: {Common VQ Curves} Bus Vmin Vmax Vstep . . . . . . . . {End Common VQ Curves} where, Bus bus number (or name or node equipment name) for which the VQ curve is to be computed. Vmin the minimum p.u. voltage for the VQ curve. Vmax the maximum p.u. voltage for the VQ curve. Vstep the p.u. voltage step size for the VQ curve. Similarly, the VQ curves that will be computed only in pre-contingency case(s) are specified by a group of records as: {Pre-contingency VQ Curves} Bus Vmin Vmax Vstep . . . . . . . . {End Pre-contingency VQ Curves}

[VSAT 9.0 Modal Analysis Parameter] Number of computed modes = 3 Print bus participations = Yes Print left eigenvectors = No Print right eigenvectors = No Maximum number of printed participations = 20 Minimum value of printed participations = 0.001 Complex shift in Jacobian = 0.0,0.0 Tolerance for eigen solution = 0.0005 Include voltage-dependent loads in Jacobian = No [End]

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The VQ curves that will be computed only for a specific contingency are specified by a group of records as: {Contingency ’Ctg-name’ VQ Curves} Bus Vmin Vmax Vstep . . . . . . . . {End Contingency ’Ctg-name’ VQ Curves}

where Ctg-name is the name of the contingency (in single quotes). One such group needs to be specified for each contingency of interest. The end of the VQ curve data is specified by the record: [End]

Example

The following example contains the definition of VQ curve data (for contingency ‘A 6’).

8.21 Control Mode File

This file includes a set of two- and three-winding transformers whose tap control mode should be modified from that specified in the powerflow data. The first record in this file must be: [VSAT 10.x Control Mode] Optional description record(s) can be included in the file as: {Description} line 1 of description line 2 of description … {End description} The two-winding transformers whose taps should be locked are specified by the following group of records: {Locked 2W Transformers}

[VSAT 9.0 VQ Curve] {Contingency 'A 6' VQ Curves} 14 0.6 1.1 0.001 19 0.6 1.1 0.001 13 0.6 1.1 0.001 {End Contingency 'A 6' VQ Curves} [End]

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Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV1:kV2 Include Transformer = from-bus to-bus 'ckt-id' Exclude area = area-list Exclude zone = zone-list Exclude bus = bus-list Exclude kV = kV1:kV2 Exclude Transformer = from-bus to-bus 'ckt-id' {End Locked 2W Transformers} After the above records for all locked two-winding transformers, the manual two-winding transformers are specified by the following group of records: {Manual 2W Transformers} Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV1:kV2 Include Transformer = from-bus to-bus 'ckt-id' Exclude area = area-list Exclude zone = zone-list Exclude bus = bus-list Exclude kV = kV1:kV2 Exclude Transformer = from-bus to-bus 'ckt-id' {End Manual 2W Transformers} The three-winding transformers whose taps should be locked are specified by the following group of records: {Locked 3W Transformers} Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV1:kV2 Include Transformer = prim-bus sec-bus ter-bus 'ckt-id' Exclude area = area-list Exclude zone = zone-list Exclude bus = bus-list Exclude kV = kV1:kV2 Exclude Transformer = prim-bus sec-bus ter-bus 'ckt-id' {End Locked 3W Transformers} After the above records for all locked three-winding transformers, the manual three-winding transformers are specified by the following group of records: {Manual 3W Transformers} Include area = area-list Include zone = zone-list Include bus = bus-list Include kV = kV1:kV2 Include Transformer = prim-bus sec-bus ter-bus 'ckt-id'

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Exclude area = area-list Exclude zone = zone-list Exclude bus = bus-list Exclude kV = kV1:kV2 Exclude Transformer = prim-bus sec-bus ter-bus 'ckt-id' {End Manual 3W Transformers} Special control mode and parameters of phase shifters can be specified using the following records {2W Phase Shifter Control Settings} from-bus to-bus 'ckt-id',Amax,Amin,Pmax,Pmin,dAmax dAmin dPmax dPmin . . . . . . . . . . . . . . . . . . . . . . {End 2W Phase Shifter Control Settings} Where:

Amax Upper limit of phase shift angle in degree Amin Lower limit of phase shift angle in degree Pmax Upper limit of controlled real power in MW Pmin Lower limit of controlled real power in MW dAmax Relative post-contingency upper limit of phase shift angle in degree dAmin Relative post-contingency lower limit of phase shift angle in degree dPmax Relative post-contingency upper limit of controlled real power in MW dPmin Relative post-contingency lower limit of controlled real power in MW When Amax, Amin, Pmax, or Pmin is not inputted, the parameter in the powerflow will be respected.

dAmax and dAmin are relative to the phase shift angle in the pre-contingency solution. The phase shift angle will also be limited by Amax and Amin. When dAmax/dAmin is not inputted, Amax/Amin will be respected. dPmax and dPmin are relative to the MW flow across the phase shifter in the pre-contingency solution. When dPmax/dPmin is not inputted, Pmax/Pmin will be respected. The end of the control mode data is specified by the record: [End] As in other VSAT data files, buses can be specified by their number or name depending on the “Name Option” in the Parameter data.

Note that:

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(1) Transformers with locked control flag (0) for their tap movement in the powerflow data are always

locked. (2) A locked transformer specified in this data file will have its taps locked in both pre- and post-

contingency powerflow solution. (3) A manual transformer specified in this data file will have its taps locked in post-contingency

powerflow solution. For pre-contingency powerflow solution, however, the taps are allowed to move for the set control mode.

(4) Unlocked transformers in pre- and/or post-contingency control a bus voltage depending on the

value of the Adjust ULTCS for voltage control parameter in the Parameter file. (5) When a three-winding transformer is locked according to this file, all three taps are locked. Example

The following example contains the definition of control mode data. The five transformers (3 two-winding and 2 three-winding) included in this file will have their taps enabled for voltage control only in pre-contingency analysis. For post-contingency analysis, these taps will be locked.

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8.22 System Protection Schemes (SPS) File This file specifies the System Protection Schemes or Remedial Action Schemes, which apply protection or control actions when triggering conditions are met.

8.22.1 General

Each SPS has the following attributes:

(1) Name (2) Status: On or Off. An SPS with Off status will not act (it is ignored by VSAT). (3) Mode: Auto or Manual.

• Auto SPS can represent automatic SPS.

• Manual SPS can represent Remedial Action Plans or operation procedures, which are applied manually by the operators.

(4) Schemes: Each scheme has a set of triggering conditions and a set of actions. Different schemes of

an SPS are independent from each other. Each SPS Scheme has the following attributes:

(1) Priority: Schemes with higher priority will act before the ones with lower priority. Schemes with

the same priority will act at the same time. (2) Gates: Gates evaluate conditions that can be used later in trigger definitions:

• Each scheme may have several gates.

• Each gate may have several conditions.

• The conditions of a gate must can be evaluated logically (AND, OR, NOT relation) or arithmetically (>,>=,<,<=,=,!= relation)

• Conditions of pre-contingency gates are evaluated only in the pre-contingency. In

[VSAT 9.0 Control Mode] {Description} Sample control mode data {End Description} {Manual 2W Transformers} 100 101 '1' 100 102 ‘1’ 200 201 ‘1’ {End Manual 2W Transformers} {Manual 3W Transformers} 300 301 302 'T1' 400 401 402 'T1' {End Manual 3W Transformers} [End]

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the post-contingency, the pre-contingency value of the gate is used.

(3) Trigger: These are conditions that trigger the SPS action defined in a Scheme:

• Each scheme may have several triggers.

• Each trigger may have several conditions.

• All conditions of a trigger must be met for SPS to act (AND relation)

• Conditions of one or more triggers must be met for SPS to act (OR relation) (4) Stage: Each stage in a Scheme may have one or more actions that are triggered when conditions

of one or more triggers are met. All actions of one stage occur at the same time. Stages of each SPS Scheme act in the order specified, i.e., the first stage acts first, then, if the trigger conditions are still met, the second stage acts, and so on.

The following describes the conditions and actions of SPS.

8.22.2 Conditions

A condition is what an SPS senses from the system in order to activate the SPS actions. Description of a condition consists of: (1) Type: Measured quantity, e.g., bus voltage, branch flow, generator status, etc. (2) At: Location of measurement, e.g. bus X, branch Y-Z, etc. (3) Setting: Value or value range for the measured quantity. The condition is met if the measured

quantity is equal to, or within the range of, the Setting.

Multiple conditions can be defined for one Trigger. The SPS actions occur when all conditions of one trigger are met.

8.22.3 Actions

An action is what an SPS will do if the triggering conditions are met. Definition of an action consists of: (1) Type: Actions such as tripping branch, shedding load, etc. (2) At: Location of action, e.g. bus X, branch Y-Z, etc. (3) Setting: Value or setting of the action, e.g., % or MW of load shedding.

Some actions don’t have a setting. Multiple actions can be defined for one Stage. All actions of each stage operate simultaneously. Note that if a pre-contingency system condition (maybe any point in a transfer analysis) triggers an SPS action, the SPS action will be applied but the action will be ignored for all subsequent transfer analysis including at pre- and post-contingency system conditions.

8.22.4 SPS Data Format

The format of SPS data for VSAT is similar to other data files and the general rules of VSAT data files apply to this data. The first record of the SPS data file must be:

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[VSAT 7.0 SPS]

There are no comment lines (blank or /) allowed before this line. Optional description record(s) can be included in the file as: {Description} line 1 of description line 2 of description … {End description} Each SPS in the data is specified with a group of records identified by: [SPS] ”SPS data” [END SPS] SPS data includes the SPS name, status, mode, and one or more schemes, which are specified by the following records: SPS Name = ‘SPS_name’ SPS Status = On | Off SPS Mode = Auto | Manual {Scheme} ”Scheme data” {End Scheme} where

• Default for SPS Name is ‘No. nn’ where nn is the SPS number.

• Default for SPS Status is On.

• Default for SPS Mode is Auto. Scheme data includes priority and one or more triggers and one or more stages according to the following. Priority is specified by the following command: Scheme Priority = N Default is 1. Higher N means higher priority and zero or negative priority indicates that the scheme is Off. Each trigger is specified by the following group of records: {Trigger} Condition = type; At = location; Setting = . . .

Condition = type; At = location; Setting = . . . Condition = type; At = location; Setting = . . .

{End Trigger}

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The Condition records are described below. For an SPS to act, all conditions of one trigger must be met (conditions of each trigger are “AND”-ed and triggers of each SPS are “OR”-ed). A gate is specified by the following group of records: {Gate}

Name = Gate_Name Type = Type_Name Condition = type; At = location; Setting = . . . Condition = type; At = location; Setting = . . . Condition = type; At = location; Setting = . . .

{End Gate} A pre-contingency gate has a similar structure except for the first line: {Gate Pre-contingency}

Name = Gate_Name Type = Type_Name Condition = type; At = location; Setting = . . . . . .

{End Gate} In the above, Name and Type are mandatory commands. Gate_Name is a text string to define the Gate name. Type_Name is a text string equal to one of the following:

‘AND’ - as many conditions as required can be included.

‘OR’ - as many conditions as required can be included.

‘NOT’ - only one condition can be included.

‘=’ - exactly two conditions must be included.

‘!=’ - exactly two conditions must be included.

‘>’ - exactly two conditions must be included; condition order is important: Output is true if condition-1 is greater than condition-2.

‘>=’ - exactly two conditions must be included; condition order is important: Output is true if condition-1 is greater than or equal to condition-2.

‘<’ - exactly two conditions must be included; condition order is important: Output is true if condition-1 is less than condition-2.

‘<=’ - exactly two conditions must be included; condition order is important: Output is true if condition-1 is less than or equal to condition-2.

Gates are mainly used to perform logical operations of Trigger conditions defined for the SPS scheme. Notes: (1) Subsequent gates (and triggers) can use the output of previous gates (recursive use).

• In order to use a Condition = Gate in a gate or trigger, the gate in the condition must have been previously defined for the SPS scheme.

(2) In most ways, triggers are exactly like gates; however, the following exceptions exist:

• Only triggers will activate SPS stages; a gate whose output becomes true does nothing.

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• Triggers do not have restrictions on conditions associated with them, while gates may have (such as NOT, >, etc.).

• There is no Type definition in triggers; AND operation is assumed if multiple conditions are defined in a trigger.

• A trigger cannot be named; its output cannot be used in another trigger or gate. (3) Gate outputs cannot be used between different SPS schemes; i.e. a gate defined in one SPS scheme

cannot be used in another SPS scheme. (4) When using a mathematical comparison Type (‘=’, ‘!=’, ‘>’, ‘>=’, ‘<’, and ‘<=’) in a Gate, the

following requirements must be met:

• All conditions specified must contain a numerical setting, such as in the “Condition = Bus kV”. Therefore, “Condition = Branch Status”, “Condition = Contingency”, “Condition = Gate”, etc. cannot be used.

• In order to start the comparison, all conditions must be true, i.e., the variables specified in the conditions must be within the settings.

• The comparison is performed using the actual values of the variables.

(5) A pre-contingency gate checks the conditions in the pre-contingency powerflow.

See examples later for further explanation. Each Stage is specified by the following group of records: {Stage} Action = type; At = location; Setting = . . . Action = type; At = location; Setting = . . . Action = type; At = location; Setting = . . . {End Stage} The Action records are described below. Stages of each SPS act one at a time, in the order specified in the data, i.e., the first stage acts first, then if needed, the second stage acts, and so on. All actions of one stage occur at the same time. The end of the SPS data file is specified by the record: [End]

SPS Conditions The following are descriptions of the SPS Trigger Conditions supported.

Voltage at bus busI is between kVlo and kVhi kV (condition is not met if busI is out-of-service): Condition = Bus kV; At = busI; Setting = kVlo kVhi Dev_flag

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Voltage at bus busI is between Vlo and Vhi pu (condition is not met if busI is out-of-service): Condition = Bus pu V; At = busI; Setting = Vlo Vhi Dev_flag

Generation at bus busI (MW output of all units) is between Plo and Phi MW (condition is not met if busI is out-of-service): Condition = Bus MW Generation; At = busI; Setting = Plo Phi Dev_flag

Shunt (sum of fixed shunt, switched-on blocks of switchable shunt, and net output of SVC) at bus busI is between Qlo and Qhi MVAr nominal (condition is not met if busI is out-of-service): Condition = Bus MVAr Shunt; At = busI; Setting = Qlo Qhi Dev_flag

Status of line or transformer from-bus, to-bus, id is In or Out: Condition = Branch Status; At = from-bus to-bus ‘id’; Setting = In | Out

MW flow on line or transformer from-bus, to-bus, id is between Plo and Phi MW, measured at from-

bus, towards to-bus (condition is not met if the branch is out-of-service): Condition = Branch MW; At = from-bus to-bus ‘id’; Setting = Plo Phi Dev_flag

MVAr flow on line or transformer from-bus, to-bus, id is between Qlo and Qhi MVAr, measured at from-bus, towards to-bus (condition is not met if the branch is out-of-service): Condition = Branch MVAr; At = from-bus to-bus ‘id’; Setting = Qlo Qhi Dev_flag

MVA flow on line or transformer from-bus, to-bus, id is between Flo and Fhi MVA, measured at from-

bus, towards to-bus (condition is not met if the branch is out-of-service): Condition = Branch MVA; At = from-bus to-bus ‘id’; Setting = Flo Fhi Dev_flag

Current in Ampere on line from-bus, to-bus, id is between Ilo and Ihi Amps, measured at from-bus, towards to-bus (condition is not met if the line is out-of-service): Condition = Branch AMP; At = from-bus to-bus ‘id’; Setting = Ilo Ihi Dev_flag

Loading (current) on line or transformer from-bus, to-bus, id is between lo% and hi% of its number N rating in the powerflow data, measured at from-bus, towards to-bus (condition is not met if the branch is out-of-service): Condition = Branch Loading; At= from-bus to-bus ‘id’; Setting = lo hi N

Reactance of branch1 from-bus, to-bus, id is between Xlo and Xhi pu (condition is not met if the line is out-of-service): Condition = Line Reactance; At= from-bus to-bus ‘id’; Setting = Xlo Xhi Dev_flag

MW flow of interface int_name (defined in the Interface and Circuit file) is between Plo and Phi MW (condition is not met if all branches of the interface are out-of-service):

1 The branch must not be a sectional line, but may be a transformer.

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Condition = Interface MW; At = 'int_name'; Setting = Plo Phi Dev_flag

MVAr flow of interface int_name (defined in the Interface and Circuit file) is between Qlo and Qhi MVAr: Condition = Interface MVAr; At = 'int_name'; Setting = Qlo Qhi Dev_flag

MVA flow of interface int_name (defined in the Interface and Circuit file) is between Flo and Fhi MVA: Condition = Interface MVA; At = 'int_name'; Setting = Flo Fhi Dev_flag

Status of generator at busG id is In or Out:

Condition = Generator Status; At = busG ‘id’; Setting = In | Out

Status of generator at busG id is In or Out: Condition = Generator Status; At = busG ‘id’; Setting = In | Out MVAr output of generator at busG id is between Qlo and Qhi MVAr: Condition = Generator MVAr; At = busG ‘id’; Setting = Qlo Qhi Dev_flag Contingency ctg_name has occurred (ctg_name is the name of one contingency specified in the Contingency file): Condition = Contingency; At = ‘ctg_name’

Note that some conditions have an optional parameter Dev_flag. If no value was specified (default), the current value will be checked. The other possible values for this parameter are: ‘DEV’: The deviation from the pre-contingency solution value to the current value will be

examined, if it is within the specified range, the condition is true. ‘DEV_PREULTC’: The deviation from the pre-contingency solution value to the pre-ULTC

solution value will be examined, if it is within the specified range, the condition is true. To use this parameter, the Perform both ULTC enable/disable computations option in the parameter file needs to be true.

SPS Actions

The following are descriptions of the SPS Actions supported. Switch on (off) N banks of capacitor (reactor) of the switchable shunt at bus busI id:

Action = Switch Shunt Banks; At = busI ‘id’; Setting= N

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When N is positive, first reactor banks are switched off, if any, then capacitor banks are switched on, for a total of N banks. When N is negative, first capacitor banks are switched off, if any, then reactor banks are switched on, for a total of N banks. If the Mode of switchable shunt is 1, it is set to 0 (frozen) after SPS switches the banks. If the Mode of switchable shunt is greater than 1, it is not switched by SPS. Trip line or transformer from-bus, to-bus, id: Action = Trip Branch; At = from-bus to-bus ‘id’ Connect line or transformer from-bus, to-bus, id: Action = Connect Branch; At = from-bus to-bus ‘id’ Change reactance of branch2 from-bus, to-bus, id to Xnew: Action = Change Line Reactance; At= from-bus to-bus ‘id’; Setting= Xnew

Trip generator at bus busG id: Action = Trip generator; At = busG ‘id’ Block (disarm) AGC action for generators at buses bus1, bus2, bus3: Action = Suspend AGC; At = bus1, bus2, bus3 Decrease generation at buses bus1, bus2, bus3 to MWnew (if generation is less than MWnew, it won’t be increased; generation of each unit won’t be reduced below its Pmin): Action = Decrease generation; At = bus1, bus2, bus3; Setting = MWnew Decrease load at buses bus1, bus2, bus3 to MWnew at constant power factor (if load is less than MWnew, it won’t be decreased): Action = Decrease load; At = bus1, bus2, bus3; Setting = MWnew Shed load at buses bus1, bus2, bus3 by MWshed at constant power factor (if a load is less than MWshed, it will be reduced to zero): Action = Shed load MW; At = bus1, bus2, bus3; Setting = MWshed Shed load at buses bus1, bus2, bus3 by P.C.shed% at constant power factor (P.C.shed, must be between 0 and 100): Action = Shed load %; At = bus1, bus2, bus3; Setting = P.C.shed

2 The branch must not be a sectional line but may be a transformer.

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Change the phase shifting angle of phase shifter from-bus, to-bus, id by ANG degrees (the phase shifter will be locked after the adjustment): Action = Adjust Phase Shifter; At = from-bus to-bus ‘id’; Setting = ANG Change the control settings of phase shifter from-bus, to-bus, id: Action = Change Phase Shifter Settings; At = from-bus to-bus ‘id’; Setting =

Amax,Amin,Pmax,Pmin,dAmax dAmin dPmax dPmin

Refer to section 8.21 (Control Mode File) for the details of the parameter list of this action.

Example

In the following, both Gates include a mathematical comparison (‘>’). In the first Gate, non-numerical conditions (branch status) are included and thus the Gate is incorrectly defined. Execution of this Gate will result in an error. In the second Gate, numerical conditions (bus kV) are included; thus the definition is correct. When this Gate is executed, however, results may still vary:

• If V(bus 100) = 505 kV and V(bus 200) = 510 kV, both conditions are True. The mathematical comparison will be performed and the output of the Gate will be False.

• If V(bus 100) = 498 kV and V(bus 200) = 510 kV, the first condition is False. The mathematical comparison will not be performed and an error will result from the execution of the Gate.

The following Gate defines an AND operation, i.e., the output of the Gate is true if all three branches are out of service. The following Gate defines an OR operation, i.e., the output of the Gate is true if ‘AND Operation’ is true or the generator at bus 101 ‘1’ is out of service.

{Gate} Name = 'AND Operation' Type = 'AND' Condition = branch status ; At = 100 101 ‘1’; Setting = Out Condition = branch status ; At = 100 201 ‘1’; Setting = Out Condition = branch status ; At = 100 301 ‘1’; Setting = Out {End Gate}

{Gate} Name = 'OR operation' Type = 'OR' Condition = Gate ; At = 'AND Operation' ; Setting = True Condition = Generator Status; At = 100 ‘1’; Setting = Out {End Gate}

{Gate} Name = 'Incorrect Comparison' Type = '>' Condition = branch status ; At = 100 101 ‘1’; Setting = Out Condition = branch status ; At = 100 201 ‘1’; Setting = Out {End Gate} {Gate} Name = 'Correct Comparison' Type = '>' Condition = Bus kV ; At = 100 ; Setting = 500.0 550.0 Condition = Bus kV ; At = 200 ; Setting = 500.0 550.0 {End Gate}

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The following example shows how a Gate output is used in a Trigger. The following is an example of an SPS that performs load shedding. The trigger condition is that any of loading in three lines specified is high, as well as contingency CTG #1 occurs. The SPS action is to shed all load at bus 1000.

{Trigger} Condition = Gate ; At = 'OR operation' ; Setting = True {End Trigger}

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8.23 Remedial Control File

This file, required for Remedial Action computations, specifies the available controls that can be used to remove security violations. The first record in this file must be: [VSAT 4.x Remedial Control] A name for the control can be specified by record:

[SPS] SPS Name = 'Load Shedding' SPS Status = On SPS Mode = Auto {Scheme} Scheme Priority = 500 {Gate} Name = 'GT1' Type = 'AND' Condition = Branch MVA; At = 205 305 '1'; Setting = 1076.000 9999 {End Gate} {Gate} Name = 'GT2' Type = 'AND' Condition = Branch MVA; At = 285 286 ‘1'; Setting = 1076.000 9999 {End Gate} {Gate} Name = 'GT3' Type = 'AND' Condition = Branch MVA; At = 380 390 '1'; Setting = 1076.000 9999 {End Gate} {Gate} Name = 'GCS1' Type = 'OR' Condition = Gate ; At = 'GT1' ; Setting = True Condition = Gate ; At = 'GT2' ; Setting = True Condition = Gate ; At = 'GT3' ; Setting = True {End Gate} {Gate} Name = 'CTG #1' Type = 'OR' Condition = Contingency ; At = 'CTG #1' {End Gate} {Gate} Name = 'Trigger Condition' Type = 'AND' Condition = Gate ; At = 'GCS1'; Setting = True Condition = Gate ; At = 'CTG #1'; Setting = True {End Gate} {Trigger} Condition = Gate ; At = 'Trigger Condition'; Setting = True {End Trigger} {Stage} Action = Decrease load; At = 1000; Setting = 0.000 {End Stage} {End Scheme} [END SPS]

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Remedial Control Name = 'rc-name'

where rc-name is a 16-character name for remedial control data. Optional description record(s) can be included in the file as: {Description} line 1 of description line 2 of description … {End description} Control of generator voltage settings is specified by the following command: Control generator voltage settings = Yes | No

When Yes is specified, generator voltage settings may be adjusted with remedial actions. When No is specified (default), they are not adjusted. Control of SVC and continuous shunt voltage settings is specified by the following command: Control SVC/shunt voltage settings = Yes | No

When Yes is specified, SVC/shunt voltage settings may be adjusted with remedial action. When No is specified (default), they are not adjusted. Control of switchable shunt capacitors and reactors is specified by the following command: Control switchable shunts = Yes | No

When Yes is specified, shunts may be switched in or out with remedial action. When No is specified (default), they are not switched. Control of transformer tap settings is specified by the following parameter: Control transformer tap settings = Yes | No

When Yes is specified, transformer taps may be adjusted with remedial action. When No is specified (default), they are not adjusted. Control of generator outputs (generation re-dispatch) is specified by the following parameter: Control generation dispatch = Yes | No

When Yes is specified, generators may be re-dispatched with remedial action. When No is specified (default), they are not dispatched. Control of loads (load shedding) is specified by the following command: Control load shedding = Yes | No

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When Yes is specified, loads may be shed with remedial action. When No is specified (default), they are not shed. Available controls for the remedial action are specified in one or more control groups. Each group includes one kind of control device and has a control priority (an integer number). Devices of groups with higher priority are used before those with lower priority. If the priority is 0, the group is ignored (its devices are not used for remedial action.) Some groups have a control mode to specify whether the group is used for Preventive control, Corrective control or both. The control groups are specified as follows. A group for generator voltage control data begins with record: {Generator voltage control} The group’s priority is specified by (the first record following the above record): Priority = p

p must be greater than zero, and Control generator voltage settings must be set to Yes, for generators in this group to be used with remedial action. This group is used for preventive control only. The generators belonging to this group are specified by any combination of (see Section 8.1.4 on rules for entering the data): Include area = area-list






This group ends with record: {End Generator voltage control} A group of SVC/shunt voltage control data begins with record: {SVC/shunt voltage control} The group’s priority is specified by (the first record following the above record): Priority = p

p must be greater than zero, and Control SVC/shunt voltage settings must be set to Yes, for SVC/shunts in this group to be used with remedial action. This group is used for preventive control only. The SVCs and continuous shunts (switchable shunts with mode 2 or 3) belonging to this group are specified by any combination of: Include area = area-list


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This group ends with record: {End SVC/shunt voltage control} A group of switchable shunt (capacitor and reactor) control data begins with record: {Switchable shunt control} The group’s priority is specified by (the first record following the above record): Priority = p

p must be greater than zero, and Control switchable shunts must be set to Yes, for shunts in this group to be used with remedial action. The group’s control mode is specified by one of the following three commands: Control mode = Preventive only Control mode = Corrective only Control mode = Preventive and Corrective The default is Preventive and Corrective. The switchable shunts (with mode 0 or 1) belonging to this group are specified by any combination of: Include area = area-list






This group ends with record: {End switchable shunt control} A group of transformer tap control data begins with record: {Transformer tap control} The group’s priority is specified by (the first record following the above record): Priority = p

p must be greater than zero, and Control transformer tap settings must be Yes, for transformer taps in this group to be used with remedial action.

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The group’s control mode is specified by one of the following three commands: Control mode = Preventive only Control mode = Corrective only Control mode = Preventive and Corrective The default is Preventive and Corrective. The transformers belonging to this group are specified by any combination of: Include area = area-list






This group ends with record: {End Transformer tap control} A group for generation re-dispatch control data begins with record: {Generation re-dispatch control} A name for the group must be specified by: Generation re-dispatch group name = 'group-name'

The group’s priority is specified by (the first record following the above record): Priority = p

p must be greater than zero, and Control generation dispatch must be set to Yes, for generator in this group to be used with remedial action. The group’s control mode is specified by one of the following three commands: Control mode = Preventive only Control mode = Corrective only Control mode = Preventive and Corrective The default is Preventive and Corrective. The generators belonging to this group are specified by any combination of: Include area = area-list


Include bus = bus-list Include unit = bus ‘id’ Exclude area = area-list


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Exclude bus = bus-list Exclude unit = bus ‘id’

The step size in MW for adjusting the generation in this group is specified by: Step size = MW-step

MW-step must be greater than zero. The range in MW for adjusting the generation in this group is specified by: Maximum increase = MW-increase

Maximum decrease = MW-decrease

The dispatch mode of this group is specified by: Dispatch Mode = Increase only

Dispatch Mode = Decrease only

Dispatch Mode = Increase and Decrease

The scale mode of this group is specified by: Scale generation = MW output

Scale generation = MW reserve It should be noted that when MW reserve is specified, out of service generators will be turned on when the generation of the group is scaled up. In service generators will not be turned off despite the scale mode. The load/generation mismatch caused by dispatching this group is met by another generation re-dispatch group (balance group). The balance group can be automatically chosen by the program based on sensitivities, or specified by the user using the following record: Balance group = 'group-name-1'

In order for generation re-dispatch control to work, there must be at least two generation re-dispatch groups specified. This group ends with record: {End generation re-dispatch control} A group for load shedding control data begins with record: {Load shedding control} A name for the group must be specified by: Load shedding group name = 'group-name'

The group’s priority is specified by (the first record following the above record): Priority = p

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p must be greater than zero, and Control load shedding must be set to Yes, for loads in this group to be used with remedial action. This group is used for corrective control only. The loads belonging to this group are specified by any combination of: Include area = area-list





Exclude bus = bus-list The loads included in each group are shed together in up to four blocks. The block sizes are specified in percentage as: Load shedding percentage = blk1, blk2, blk3, blk4

All loads in this group are first shed by blk1% (e.g., if blk1 is 25, 25% of every load is shed first), then, if needed, the loads are shed by blk2%, blk3%, and finally blk4%. By default, blk1 = 100, blk2 = blk3 = blk4 = 0. The load/generation mismatch caused by load shedding, similar to load/generation outages, is met by the dispatch option for contingencies. This group ends with record: {End load shedding control} The end of the remedial control data is specified by the record: [End]

Example

The following example contains the definition of remedial control data.

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8.24 Sensitivity Parameter File

This file is used to specify the parameters for the Remedial Action computation. The first record in this file must be: [VSAT 4.x Sensitivity Parameter] Each parameter is specified on one record as follows. The remedial action can be applied to respect three kinds of security criteria, namely VS margin, voltage limit, and VAr reserve. However, it may be desirable to ignore one or two of these criteria and find the remedial action for the remaining criteria. Criteria can be ignored by one of the following commands: Remedy margin violations = Yes | No

[VSAT 9.0 Remedial Control] {Description} Sample remedial control data {End Description} Remedial Control Name = 'Sample Control' Control generator voltage settings = No Control SVC/shunt voltage settings = No Control switchable shunts = Yes Control transformer tap settings = No Control load shedding = Yes {Switchable shunt control} Priority = 2 Control mode = Preventive and Corrective Include area = 1:2 {End switchable shunt control} {Load shedding control} Load shedding group name = 'Bus 14 load' Priority = 4 Include bus = 14 Load shedding percentage = 25 25 25 25 {End load shedding control} {Load shedding control} Load shedding group name = 'Bus 19 load' Priority = 5 Include bus = 19 Load shedding percentage = 25 25 25 25 {End load shedding control} {Load shedding control} Load shedding group name = 'Bus 11 load' Priority = 6 Include bus = 11 Load shedding percentage = 25 25 25 25 {End load shedding control} [End]

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Remedy voltage violations = Yes | No

Remedy VAr reserve violations = Yes | No

The interpretation of these commands is straightforward. The default is Yes. Enabling the Corrective control, after the Preventive controls are exhausted, is specified by: Apply corrective control = Yes | No

When Yes is specified, the Corrective control is enabled. When No is specified (default), the Corrective control is disabled. The controls are chosen in the order of their sensitivities. The most sensitive control is chosen first. If this control is not sufficient for resolving the violation, or is rejected because it is not effective or causes other violations, the next sensitive control is chosen. The process continues until the violation is completely resolved or the sensitivity of the remaining controls becomes smaller than thresholds specified by the following commands: Threshold for load sensitivity = lst Threshold for shunt sensitivity = sst Threshold for tap sensitivity = tst Threshold for voltage sensitivity = vst The default value for all of the above four commands is 0.001. When a control is chosen to resolve voltage limit or VAr reserve violations, that control will be accepted (considered effective) if the resulting improvement in the violation index is greater than the threshold given by: Threshold for voltage improvement = vit Threshold for VAR reserve improvement = qit The defaults for vit and qit are 0.0001 pu and 2.0 MVAr respectively. Some of the controls may be ineffective in removing the violations. During the trials the number of ineffective controls of each type (e.g. switchable shunts) is counted. When this number becomes larger than a maximum value, the rest of the controls of that type are skipped (even if their sensitivities are larger than specified thresholds.) This maximum number is specified by: Maximum trials for ineffective controls = max-trials

The default is 3. The following command is used to request that the powerflow case, after the Preventive controls are applied, be saved in a PFB file: Save PFB with preventive controls = Yes | No

The default is No. Under severe conditions, the post-contingency powerflow may not solve even before applying the stress. In these cases, the parameterized method is used to simulate contingencies. In this method, an outage is

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considered as a continuous process by using a continuation parameter. The parameter changes from 1 which corresponds to pre-contingency case, to zero which corresponds to post-contingency case. The parameter-voltage curves of all severe contingencies are traced to identify the most severe contingency. The step size used to trace the parameter-voltage curves is specified by: Step size for contingency parameter = cp-step

The default is 0.03. During the remedial action determination process, if the stability margin is less than the specified MW/MVAr stress, the stability limit is found by applying the stress in discrete steps. The step size for stressing the system is specified by: Step size for stress = st-step

st-step is specified in percentage. The default is 10%. When the ULTC tap settings are used as a remedial measure, each tap is adjusted by one, two, or more steps. The limit for the size of each tap adjustment is specified by: Step size for tap adjustment = tp-step

The default is 0.02. When generator, SVC and continuous shunt voltage settings are used as remedial measures, they are adjusted in discrete steps. The limit for the size of each voltage adjustment is specified by: Step size for voltage adjustment = vl-step

The default is 0.02 pu. When generator, SVC and continuous shunt voltage settings are used as remedial measures, they are kept within the voltage limits specified in the Criteria file. If the criteria data does not specify limits for a particular bus, the following limits are applied to the voltage settings for that bus: Voltage setting upper limit = Vhi

Voltage setting lower limit = Vlo

The defaults for Vhi and Vlo are 1.08 and 0.92 pu respectively. In order to choose among different kinds of controls with the same priority, scaling factors are needed for sensitivity of each kind of control device in order to make them unit-less and compare them with each other. These scaling (or weighting) factors are specified by: Weighting factor for shunt sensitivity = swf The default is 10.0 1/MVAr. Weighting factor for tap sensitivity = twf The default is 0.01 1/pu.

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Weighting factor for voltage sensitivity = vwf The default is 0.01 1/pu. This is the weighting factor for generator, SVC and continuous shunt voltage setting. The end of the sensitivity parameter data is specified by the record: [End] Example

The following example contains the definition of sensitivity parameters.

8.25 Generator Coupling File

This file provides data for dispatching generation according to the Combined Cycle Power Plant (CCPP) model in the transfer analysis. The first record in this file must be: [VSAT 9.0 Generator Coupling] Optional description record(s) can be included in the file as:

[VSAT 9.0 Sensitivity Parameter] Remedy margin violations = Yes Remedy voltage violations = No Remedy VAr reserve violations = No Apply corrective control = Yes Save PSF with preventive controls = No Threshold for load sensitivity = 0.001 Threshold for shunt sensitivity = 0.001 Threshold for tap sensitivity = 0.001 Threshold for voltage sensitivity = 0.001 Threshold for voltage improvement = 0.0001 Threshold for VAR reserve improvement = 2.0 Maximum trials for ineffective controls = 3 Step size for contingency parameter = 0.03 Step size for stress = 10 Step size for tap adjustment = 0.02 Step size for voltage adjustment = 0.02 Voltage setting upper limit = 1.08 Voltage setting lower limit = 0.92 Weighting factor for shunt sensitivity = 10 Weighting factor for tap sensitivity = 0.01 Weighting factor for voltage sensitivity = 0.01 [End]

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{Description} line 1 of description line 2 of description … {End description} A CCPP train generally is a combined cycle power plant or a group of gas/steam turbines in a combined cycle power plant whose generations are related to each others. The definition of a CCPP train begins with record: {CCPP train} A 24-character identifier should be specified for the train data by: Train name = 'identifier' Each generator that should be included in the CCPP train is specified by one of the following records: Include GT = bus-no 'unit-id' or Include ST = bus-no 'unit-id' where GT means gas turbine and ST means steam turbine. GT and ST make no difference in the computation. They are just to distinguish different types of units. After all the generators in the CCPP train are specified, the possible generation dispatches can be specified by the following record. Include Dispatch = P-unit1 P-unit2 P-unit3 …… P-unitN Auxload One record specifies one possible generation dispatch of the train. Where P-unit1 is the output of the first generator that appears in the train definition in this dispatch, P-unit2 is the output of the second generator that appears in the train definition in this dispatch, and so on. The amount of auxiliary load of this dispatch can be specified by Auxload (MW). Up to 20 generators and 50 dispatches can be defined for one CCPP train. The data for this CCPP train is terminated by record: {End CCPP train} The end of the generator coupling data is specified by record: [End] When CCPP data is provided, VSAT checks the basecase powerflow and the transfer file for possible confliction:

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(1) If the outputs of the generators in a CCPP train are in conflict with the basecase powerflow, the outputs of these generators will be re-dispatched to make them consistent with the CCPP data.

(2) All of the in-service generators of a CCPP train must be in the same generator scale/schedule group. (3) If a CCPP train is included in a generator schedule group, all the generators in the train must have

the same up-order or dn-order in this group. (4) For a generator specified in a CCPP train, its Pmax and Pmin in the powerflow data will be ignored. Note that VS margin computation (i.e., system stress performed using the Margin file) doesn’t respect the Generator Coupling File. Example

The following example contains the definition of generator coupling data.

[VSAT 9.0 Generator Coupling] {CCPP TRAIN} TRAIN NAME = 'CCPP Plant A' INCLUDE GT = 100 '1' INCLUDE GT = 101 '2' INCLUDE ST = 102 '5' INCLUDE DISPATCH = 65.0 0.0 0.0 4.0 INCLUDE DISPATCH = 0.0 65.0 0.0 4.0 INCLUDE DISPATCH = 65.0 65.0 17.0 12.0 {END CCPP TRAIN} [END]